Wouldn't it mean the gamers' mods for say StarCraft? or maybe Diablo 3? would have to be rated by the ESRB, PEGI, USK, and BBFC? And also mean that Blizzard would need to test the mod internally as would Sony (ps3) and Microsoft (Xbox 360).
As I understand, this is why Bethesda hasn't allowed pc mods to become available for consoles as of yet...