Spoil At Your Own Risk

Everyone knows about It Was His Sled, but most of the time, posting a spoiler without any warning will get you cursed, flamed, and even banned from any forum you decide to post it on. However, there are some things you just don't want to spoil, warning or otherwise.

With all the incredibly profitable uber-franchises permeating the pop-culture landscape, directors, writers, and entire companies nowadays tend to be incredibly sensitive about plot details of their upcoming books, movies, TV shows, video games, etc. getting out to the public before the release date. This is especially true on forums and other media where The Gods Themselves (series creators, staff) tend to frequent, because admins of those forums fear that any such leak might be blamed on said staff member, and so they'll be especially diligent in deleting said spoilers. Companies have been known to have lawyers troll the popular Fora of the internet, seeking out any possible sign that spoilers of their property have leaked.

Basically, the difference between an ordinary spoiler and this trope is that you can get away with posting a regular spoiler if you give sufficient warning, while someone can be punished for revealing or even discussing something that falls under this, even if they give all the warning in the world. If you post spoilers for the latest installment of Rise Of The Uber-Ultimate Hype Machine Wizards 12 before 12:01 AM on X Day Of Y Month Of Z Year, they won't just scream "Nooooooooo! You bitch! YOU BITCH!" - they'll go after you. Hard. If you were working on it in some manner... well, you likely won't be soon. So Spoil At Your Own Risk - and expect to see such spoilers running wild around the Interwebs right after said work has been released proper.

Contrast Late Arrival Spoiler.

Film
""No, Obi-Wan killed your father.""
 * Tyler Nelson was an extra and trained dancer who was intended to appear in Indiana Jones and the Kingdom of the Crystal Skull. When he blabbed spoilers about the movie, not only did he violate his nondisclosure agreement (and was thus sued), but the scenes he was a dancer in were cut from the movie.
 * Psycho implored the viewer not to release the shocking secret to friends after seeing the movie. Given that It Was His Sled, it didn't work, though it was really inevitable. Unless that was his plan all along. In fact, Alfred Hitchcock actually ordered movie theaters not to let anyone into the theater once the movie started.
 * Many of those who saw Serenity at various pre-screenings held across the U.S. were at the forefront of keeping the spoilers (and THE spoiler) under wraps as a form of self-policing.
 * When The Empire Strikes Back was being filmed, George Lucas went so far as to change the line in the script, dubbing it over in post-production, so that no one but he, James Earl Jones, Mark Hamill (who needed to react properly) and a very select group of the production crew would know Vader's relation to Luke before the premiere. Of course, that was then, and this is now.


 * There was another one related to Darth Vader. Supposedly, the scenes in Return of the Jedi with Vader outside his mask were shot with David Prowse in the makeup, finally getting his face shown onscreen. However, when being interviewed on a late night talk show, he bragged "You'll finally get to see my face!" Cue George Lucas getting very angry, and then re-shooting those scenes with a different actor, pretty much just to get back at Prowse for spoiling that Vader would be helmetless in at least one scene.
 * It's clear that David Prowse was horrible at keeping secrets, as he discussed a spoiler about Vader's relationship to Luke when he was interviewed by a small California news paper.
 * Something similar happened when Attack of the Clones was in pre-production. Lucas offered the role of teenage Anakin to Leonardo DiCaprio, who gave it away in an interview. As a result he was kicked out and Hayden Christensen got the role instead.
 * 20th Century Fox put on a big show of being VERY secretive about spoilers for The Simpsons Movie, up to and including taking steps similar to those taken by Scholastic lawyers to prevent plot details from leaking out before the movie was screened officially for critics and audiences in Springfield, Vermont, the site of the film's premiere.
 * After the mass leaks of character design sheets, script drafts, and more from the first live-action Transformers movie, some die-hard fans went as far as to hack Michael Bay's computer during filming of Revenge of the Fallen. Bay then went out of his way to announce that those working on the movie would be intentionally releasing misinformation as "leaks" to throw out red herrings for the fanbase. Of course, some speculated that the misinformation campaign itself was an attempt to cast doubt upon said leaks.

Literature

 * Most notably, the Harry Potter franchise, particularly for the last two books of the series, Harry Potter and the Half-Blood Prince, and Harry Potter and the Deathly Hallows. The company distributing the books has gone so far as to make every owner of bookstores that receive the books to sign non-disclosure agreements subjecting them to heavy fines and lawsuits if they dare speak a single word about the content of the books. Scholastic had once gone so far as to demand that readers who are accidentally sold a copy of the book not read it until the release date, though J.K. Rowling herself soon stepped in to say that those who purchased the books could read them, as long as they not spoil the contents of the book until the official release date. (Although how the prohibition would have been enforced anyway is a mystery.) Even as the editor typed these words, the authorities behind the DMCA were stalking their way through the internet, threatening site owners with legal action if their members post Harry Potter spoilers before the release date. This may end up backfiring, as the rush to clamp down after the posting of a few leaks of questionable authenticity raises suspicions about their authenticity not being so questionable after all. But then, even if they heard it first, who would have believed that The Deathly Hallows was Voldemort's sled from when he was a boy?
 * When an early, incomplete draft of the Twilight series novel Midnight Sun was leaked in 2008, the author was so frustrated by the experience that she discontinued work on it and put it on indefinite hold, famously saying that if she completed the book in her current state of mind, she'd have let the villains win.

Live-Action TV

 * A good deal of reality shows do this, swearing all the participants to secrecy and - when it comes to dating reality shows - prevent the winning couple to show up together in public until the last episode airs.
 * Comedy Central's Battlebots was filmed in front of a live studio audience, several months before the fights actually aired on television. Rumors abound of event staff actually going so far as to make each and every audience member sign non-disclosure agreements before attending the event, and administrators of Battlebots fan forums frequently deleted such spoilers if they were posted, with or without warnings. This is likely because all of the major fan forums were run by/heavily populated by Battlebots contestants, who thus had more of a vested interest in keeping the results of the competition close to their chest.
 * Rose, the first episode of the new Doctor Who, was leaked online by an insider a few weeks before it was officially broadcast. The leak was eventually traced back to an employee at the CBC who was fired over it.
 * The BBC sent out the broadcast masters of the 2005 series under a codename in an effort to keep them secret. The selected codename was an anagram of Doctor Who, and ended up being recycled as the title of the spinoff series, Torchwood.
 * Casting is also very secretive. Karen Gillan was hired to act in an upcoming production called "Panic Moon." As it so happens, "Panic Moon" is an anagram for "Companion."
 * ...said revelation (by Karen Gillan, in an interview) lead to Steven Moffat remarking in another interview that now they needed to find another way to hide future auditions. How much he was really put out by it is anyone's guess.
 * ABC was normally supportive of (or at least pretending to be oblivious to) Lost's spoiler community until the end of the third season, when a detailed plot description of the finale, including a major gamechanging cliffhanger, was posted online. ABC launched an internal investigation to find who was responsible, and showrunners Damon Lindelof and Carlton Cuse refused to do any interviews or discuss the finale until Comic-Con three months later (and then sparsely afterwards). The investigation presumably failed, as the same individual spoiled the season 4 finale as well.
 * Played straight and subverted with FOX during 24's run. During the third season, a 24 spoiler blog revealed plot summaries for upcoming episodes (even ones that hadn't been filmed yet), and spoiled a script that ended with Ryan Chappelle (the former division director of CTU in the second and third seasons) faking his death and going into hiding after a demand by Stephen Saunders. FOX understandably went loco over this, tried to shut down the blog (it didn't work) and changed the script so that Chappelle was killed off for real. In later seasons, however, fans posting on the show's official forums were able to walk onto the set of the production and take shooting scripts at will, leading to fans finding about plot threads that wouldn't be revealed for several episodes. Fox was apparently okay with this, as they never bothered to moderate or police their own board.

Professional Wrestling

 * Professional Wrestling fans are quite the opposite; they have no problems with spoilers from a taped show, as long as said spoilers are clearly marked. The WWE itself, however, is another story; they seem rather schizophrenic in their treatment of the subject, in some instances ejecting anybody who even brings a notebook to a TV taping, while at other times posting spoilers on their own official site. Their current stance seems to be somewhere in the middle; they'll allow people to take notes, and even to tape the event, but will not allow the use of cellphone cameras or laptop computers (so that, at the very least, the show won't be spoiled until after the taping is over).
 * Notably, when CM Punk delivered his incendiary post-show monologue in the summer of 2011 (in which he insulted the company and leveled several disparaging remarks at Vince Mcmahon and John Laurinitis), the taping which it occurred was one of two shows being shot that night (a week before Independence Day; WWE doesn't film on that date). Naturally, fans attending the event saw the entirety of two weeks worth of shows being filmed at once. As such, they also learned that, at the end of the second taping, Punk was rehired by the company. This led to a massive subversion of the trope when said fans leaked the information, and slammed WWE for attempting to play up the illusion that Punk had been fired (with the company "deleting" his official profile on their website and removing his social media presence).

Tabletop Games

 * Major spoilers have happened twice in Magic's history.
 * The first and most famous one was the Time Spiral spoilers, where MTGSalvation's Rancored Elf, a prominent spoiler member, received a preview of 4 cards from Time Spiral Block's first set. This happened during Dissension, nearly three whole sets before Time Spiral was due to be released (about 9 months before scheduled spoilers even begin). This happened back in 2006.
 * The second and most recent was the New Phyrexia spoiler: An entire set revealed nearly two weeks before the official spoilers were off the ground. This was after Wizards of the Coast took painstaking means to conceal if the third set of Scars of Mirrodin would be Mirrodin Pure or New Phyrexia (something the forums had been speculating for 3 months). In both cases, legal action was taken (Rancored Elf was sued and issued a Cease and Desist, and the people responsible for spoiling New Phyrexia's cards were given a very long ban from DCI-sanctioned events).

Theatre

 * Agatha Christie's play The Mousetrap, or Three Blind Mice, has a twist ending that they implore you to keep secret. Most productions of the play even bill themselves as "the longest-running secret in the history of theatre!", or variations to that effect. Most people actually obey.
 * A joke among theatreland insiders tells of an American couple going to see The Mousetrap, tipping their cabbie poorly, and having "The Butler Did It!" yelled at their departing backs. Fear not if you are spoiler-averse: there is no butler character in the Mousetrap.

Video Games

 * Kingdom of Loathing:
 * At Jick's request, a certain Easter Egg in a level 10 quest will never, ever appear on the KoLwiki. Ever. There's a filter in the in-game chat to prevent it being spoiled there, and spoiling it in the forums will get the mods all up on your ass.
 * "Riff said he'd give anyone who spoiled the end of the bees storyline in the forums a kick in the balls. Bee warned."
 * This hit BioWare in full force in the months leading up to the release of Mass Effect 3. An internal demo build of the game (comprising part of the intro mission, and a quest involving the rescue of a Krogan female) was inadvertently posted on Xbox Live then taken down a day later, and was promptly played, filmed, and uploaded to YouTube by hardcore fans. Then, even more incredibly, a group of users on the Russian Bioware Social Network cracked the internal code of the demo and found design documents that contained most (if not the entirety) of the game's plot, including morality decisions, surprise character appearances, benefits of having saved games from the previous installments and a complete rundown of every squadmate, weapon, power and location visited. Bioware employees immediately went on the defensive (saying that the documents were from a pre-alpha version of the game), going so far as to send famed internet gaming board NeoGAF a cease-and-desist letter (courtesy of Microsoft) asking not to reveal the spoilers, and permabanning anyone who made any more than a passing mention of the leaked documents. Then, a few weeks later, the official demo release was once again cracked by fans, who discovered 20 minutes worth of Codex dialogue, the game's loading screens, and dialogue for the secret character.
 * Konami understandably didn't want reviewers of Metal Gear Solid 4 revealing crucial plot spoilers in reviews before the game was released. They subsequently went as far as to prevent reviewers from "spoiling" the game's excessive mandatory install requirements and the length of its excessive cutscenes.
 * Harmonix, the developers of Rock Band and its sequel, were slammed by playtesters who violated their non-disclosure agreements by posting the entire Rock Band 2 setlist they had played (60 songs of the disc's final 84.) Needless to say, they were sued. Some think that this was a factor in Harmonix's decision to reveal the game's entire on-disc setlist at once.
 * They went on to parody this trope in the lead-up to the release of Rock Band 3, where they made an announcement that this time, they were absolutely cracking down on any potential source of setlist leaks... while somebody scrolled through the entire list of songs on a screen behind them.
 * When Scribblenauts was released early due to hundreds of Gamestops breaking the street date on its release, the moderation staff at GameFAQs went on a rampage at the site's Scribblenauts board. Any topic with gameplay discussion or anything that even appeared to be gameplay discussion was very harshly moderated, mainly because most of the posts were from people who had downloaded the ROM. They were warned for "Illegal Activities", even though a rare few amount of people had actually received perfectly legal copies from stores who had accidentally let it out early.
 * Although he has no real power to enforce it (other than perhaps through copyright), ZUN has requested that you not post the endings of the Touhou games online. However, it is enforced by many fansites, and what happens if you do it is up to whoever has authority on the site.
 * Somewhat related is the concept of street dates for games. Typically, a video game retailer will receive copies of games several days to a week before the actual release date. Without exception, these games are marked with specific release dates. If the store sells the game before the release date, it can be traced, and the retailer will be sued for breach of contract. And then, worst of all, the publisher will not allow that retailer to receive their games until after the release date (at best, at worst, they simply won't ship games to them anymore). National chains, like Gamestop, are not immune to this, and will be sued just like anyone else (and the offending employee will be fired and subject to prosecution all on their lonesome too). This is Serious Business, folks.

Web Original

 * Spoil At Your Own Risk is pretty much a rule at GameFAQs for almost every game that hasn't hit its release date, due to the site's strict anti-piracy stance and unwillingness to give its users the benefit of the doubt under any circumstances (even if a retailer broke the release date schedule).
 * This rule is law over at Mark Reads Harry Potter and Mark Does Stuff. Mark Oshiro, and many of his readers, are going through various series for the first time- so telling them plot twists from future episodes/chapters is a pretty good way to get yourself perma-banned instantly.
 * The creators of Red vs. Blue once locked a Wild Mass Guessing thread because it got an upcoming plot twist exactly right. They unlocked it later (but before the plot twist was revealed). The thread's title? ""

Other

 * The American auto industry has careened from one extreme of this to another- they invented the big-show release and pre-release security, developed it to the lengths of shipping cars in enclosed railroad boxcars and obliging dealers to soap the showroom windows in The Fifties, at which point even people with only a passing interest in cars would make an annual tour of local dealers in November just to see the new models. Now GM in particular tends to show off new models at the Detroit auto show in January with sales to begin the following fall, meaning they have only the old model to offer for almost a year.
 * The American Psychological Association has a vast number of databases of visual and auditory stimuli, along with arousal levels for each stimulus. These databases are kept closely guarded to maintain novelty among the general public, who may end up being part of their experiments at some point.