There's a new book out called Grand Theft Childhood that explores the controversies surrounding video games and violence. The two authors, both Harvard Medical School researchers (if my memory serves me), take a surprising tack in their book and argue that video games do not produce an increase in youth violence. Indeed, at one point in the book, they argue that kids who DO NOT play video games are more at risk to commit acts of violence. There's a good summary of the book's findings here.
I'm sure there are plenty who will disagree with their findings, but they are certainly interesting.