With the advent of the internet, the Caustic Critic has seen a boom in popularity. After successful acts like The Angry Video Game Nerd, many Follow the Leader type of people came on board to try their luck. Most of them failed for various reasons. Now, often this can be chalked up to lack of charisma or the kind of humor that makes such a review work. However a big reason is that they didn't realize an important idea behind making the character work.
See, oddly enough, to make a good negative review about a subject, you have to on some level enjoy the subject you're reviewing. You can still think it's a piece of shit, but there has to be a sort of fascination, a thing that makes you want to watch or play it. In a sense you are paying homage to a work by pointing out its negative points. Very often if a critic genuinely hates what they are viewing, the review descends into pure vitriol, which is neither entertaining or insightful - and generally isn't very helpful at all from a production's viewpoint. (They would like to know what they did wrong - if all they get for that question is just sarcasm and violent opinions, it's not very helpful)
Let's give an example with the guys at Riff Trax, who are both rather clever and humorous in most of their riffs. The Riff for Star Trek 5, for example was very funny and enhanced the film, even though they were bashing it. That's because they were on some level enjoying their time making it and enjoying watching the movie. The jokes and criticisms were pointed and relevant. On the other hand, their riff of the Star Wars prequels fell flat because you really got the sense that they truly did not like the movies.
Is this a hard and fast rule? No. An exceptionally eloquent reviewer can overcome this and make a good review of something he really hates on every level, but for everyone else it's something to keep in mind. Pure vitriol is not entertaining. There needs to be substance behind the hate.
Something which tends to help with this is the creation of a character or a persona which enables the critic to distance themselves for the subject of his or her reviews—to take one example, The Nostalgia Critic is a persona created by and in many ways distinct from Doug Walker, the man who portrays him. Walker has on several occasions admitted that his personal views towards some of the things he reviews are not as extreme as the Critic's (and that he even likes some of them, albeit usually in a 'so bad it's good' kind of way), but the use of a persona allows him to ramp up the vitriol for comic effect to a degree that would likely be, if not impossible, then certainly less likely to succeed if he was reviewing as himself; we expect an over-the-top and exaggeratedly vitriolic reaction from the Critic because he is an over-the-top and exaggeratedly vitriolic fictional character, while the same reaction coming from a real person acting as themselves would seem more awkward and uncomfortable, and possibly indicative of something of a lack of perspective.