You know, I've always been with the "video games, TV, and movies don't make kids violent" faction but I do believe that it gives kids ideas that they wouldn't have on their own. If a kid wants to play pranks or bully they will but if they want to do those things and they see similar (but taken up a notch) by watching or participating in the media there isn't as much 'adult' in them to think the things through to the possible conclusions...

...not that some adults aren't doing their own insanity.