Age rating is not the same thing as an age restriction, so it depends which you meant.
Attaching a suggested level of maturity to a game page is unobtrusive, and serves the point. It could even list what may be objectionable, and if someone chooses to use those to screen through the games they choose to play, that's fine.
Age restriction on the other hand is a horrible idea because:
1. It is totally unenforcable on the anonymous internet.
2. It is completly inappropriate to tell people that you don't think they have the mental capacity to deal with something.
3. It could only be applied to members, which means either a) only members can continue to play the games, or b) people will simply not get/use memeber accounts.
So, age rating makes no difference, it would only be a suggestion. Age restriction is a horrible idea.
