I'm leaving this sentence or thought incomplete, but you should already get the point I'm trying to make, so... yeah.
.....Still here? Okay, okay. So, Yeah is basically a half-assed way of explaining the Self Explanatory. The most popular version of this trope has someone going into some detail about some scenario that's going on, but not going into the implications of the events, leaving the thought incomplete in the hope that said implications are so blatantly obvious that the other person can figure it out on their own. Sure, you can explain how the Big Bad is going to take over the world, and why, but only those with an IQ of broccoli won't get why it's bad for him to succeed, and what would happen if he does.
It's also common for So Yeah to be used when it's assumed that nothing more can be said to adequately explain what's happening, or when the user just feels lazy or embarrassed about what's being said. In other words, "I've explained all I can about this, so you'll have to Figure It Out Yourself". In a media setting, it is usually done to add drama to the scene, letting the audience figure out the rest along with the other character and shuddering when they do get it, but in real life, it just comes off as a half-assed, lazy response.
Unix geeks have been know to refer to this kind of expression as "tab completion".
- In one issue of the Avengers: The Initiative, one character with super-soldier abilities was asked to reveal the source of his powers. This was neatly avoided, until the annual, where it was revealed to be the result of a special diet and exercise regimen concocted by his Mad Scientist great-grandfather. The responding quote was: "You mean... the source of your amazing strength is diet and exercise?"
- John Ritter's character in the comedy Noises Off spoke nearly entirely in 'So Yeahs' when not acting (he himself was an actor in a farce), seemingly unable to completely finish a single thought or sentence.
- An episode of Sex and the City had two of the main (female) characters visit a gay men's dance club. When they need to use the ladies' room, it turns out there's only one bathroom "because... yeah".
- The whole idea behind the Seinfeld episode "The Yada Yada" which ends ideas in very non-suggestive (not to mention Anti Climatic) ways, that leads to a lot of artificial Noodle Incidents.
- Walter of Breaking Bad has times when his "Yeah" of approval becomes a "So... Yeah".
- In Schlock Mercenary, this is Kevyn and Doctor Bunnigus' response to seeing Xinchub naked. Well, Kevyn's goes a little further (ie, on a bender).
- In a full length half hour episode of The Powerpuff Girls, the girls are forced by their Satanic enemy, Him, to solve a series of riddles and tasks of increasing danger and complexity or else their creator, the Professor, "will Pay!" The girls solve all the other tasks with great difficulty but fail in the last one...only to discover that the Professor was eating at a diner Him owned, and Him was betting the Professor a free breakfast that the girls couldn't solve all of Him's challenges. With the girls having failed the last one, the Professor will Pay...the full price of the breakfast. The Narrator ends the episode, not with the normal "And So Once Again The Day Is Saved thanks to the Powerpuff Girls!", but with, "And so...um...hmm. Yeah."
- In The Incredibles, Helen is trying (and failing) to convince herself that there is a Very Good Reason why nobody is answering her phone call radio request for landing clearance: "They must be taking a coffee break ... all at the same time ... yeah..."
- Jeff Goldblum seems to be like this in real life.
... So, yeah.