I doubt video games are the cause of violence in society. After all, people have been thinking up ways to brutally kill each other long, long before video games. My opinion is that instead of being a cause, they are an effect of a naturally violent species and instead become a safe outlet for rather repressed instincts. One friend of mine is terribly fond of the game Prototype and relishes in the chaos she can cause in the digital world. However when her brother asked her to go hunting with him she refused, saying she just didn't think she could bring herself to kill something.