Their is such thing as video game addiction and if parents don`t pay attention they may wish they had.
Here in Canada their was young man(in his teens) who ran away and died(exposure to cold).He was playing xbox live for atleast 8 hour or more a day and when his parents actual caught on it was to late.
I myself like World of warcraft,but I don`t think i could play it if I had children because of all negative talk about drugs,sex and racial s and homophobic slurs that are used on the global chat channels.
Also rating to have effect if stores like Walmart enforce their policy to not sell to minors if the E.S.R.B rating is mature.