Something else to think about.

This is an interesting video by some students from the Savannah College of Art and Design. Now I'm not a big player of video games or even on-line games, except for Parking Wars on Facebook. I use to play video games in college but that was limited to PacMan and Frogger. When my son turned 16 my wife and I allowed him to get the video game Grand Theft Auto. After he got the game I sat with him and watched him play. There was a lot of shooting, stealing of cars, and other inappropriate things going on. And imagine my delight when he "earned" enough points to become a Drug Lord. But I watched the game with him and I talked to him about what was happening. I came to understand that what he saw happening on GTA was about as real to him as it was for me when I tried to hop from log to log in Forgger.
So as with any other technology or activities your children participate in the best thing that you can do to ensure that it is appropriate for them is be involved. Don't depend on anyone or anything else to protect them, likewise don't expect to place blame on anyone else.