If you watch all three of parts of that Penn & Teller Bullshit episode on EweTube, it's actually very convincing that pretty much all current gaming research is agenda driven.
Perception is that gaming makes you a less social hermit, who is going to go nuts and kill people isn't true.
The interesting thing that came from the episode, which admittedly I've seen before I spent about a week running through Bullshit on Ewetube, is that violent crime in youths have gone down since gaming became popular, and since we all know this since it's how we all largely met, gaming is a social experience, not an anti-social one. All the biggest games today, have a social experience, look at World of Warcraft, which admittedly, is full of ragey dicks at times, or Call of Duty, etc. All big multiplayer experiences.
See, being a gamer just makes you better!!!
This all said, I am for game ratings... I don't think GTA etc should be sold to those under 18. On the other hand, I don't believe that it would necessarily be harmful to a teenager to play it, as lets face it, most of us played games that were rated for older than our ages. I mean, who didn't play Mortal Kombat when they were nine... I think in most of these things, it should be the parents prerogative. Should I ever have any, (lololfuckingol) I don't see them playing the more violent ones into their teens, depending on content. When their over 18, they can buy what they like, but I don't see the harm of an 18 so much in the hands of a 15 year old, considering I was doing the exact same thing.