http://biz.gamedaily.com/industry/fe...id=12604&rp=49
Everyone has probably heard of it by now, but here it is again. The ESRB decided to change Oblivion's rating from Teen to Mature. They say its because the game is more violent than they first thought, and because the game has been modded by third parties to include nude skins for characters.
So, basically, since any game can be modded like this, the ESRB are claiming that every game should have a rating of Mature and that the ESRB is now a redundant entity.