The only way for a "voluntary" system like the ESRB ratings to work--and keep meddlesome dogooders/controllers like Jack Thompson and Hillary Clinton (it's not just the 'extreme fundamentalist right wing" who wants to tell you how to raise your kids, don't forget "it Takes a Village" and the PMRC)--is for the participants to do what they say they will do. (Personally as a gamer and a parent, I would have no problem with stores being fined by the state for selling M games to underage kids).
Anyway, I bought the SE today at Circuit City--and I got carded. I'm 35.
Parents do need to involve themselves. However, they also don't, can't and shouldn't watch their kids (older kids) every second of every day, and if they educate themselves as to the ratings, and hear "We the industry support you as the parent", that parent wants to know the store won't sell the M-rated game to his 12 year old kid; if the voluntary method isn't enough, that's how the politicians get involved.
I did watch TV as a kid, and played video games (my first all nighter was Defender on the 2600). But I also stayed out till ten at night sometimes running around playing with the kids in the neighbourhood, so it balanced out. Kids--and adults--definitely lead a more sedentary life nowadays, and video games are a part of that (though not the only, nor necessarily the main, part).
I don't think it's bad parenting, necessarily--I think it's mostly ignorant parenting. Which is not the same thing, and ignorant in this case does not necessarily have a negative connotation. Many parents above, say, 35 or 40, still think of video games as Pac-Man and Donkey Kong, which are a far cry from GTA.
Anyway, I got it today, and the "tone" of the game appeals to me a lot more than GTA III did. I like the fact that Niko isn't a straight out bad guy (so far), and while it's violent, the rampant language and sexual comments are much more obvious to me (though I haven't encountered any actual sexual content yet). Definitely a "after the kid goes to bed" game.....like Bioshock, Crackdown, and many other games I have that I don't want him experiencing. When he gets older, but still under the M limit, if there's a game that I think is suitable for him despite being M, I'll gladly buy it for him and play with him.