Why don't they just create a digital bouncer for that particular bar and keep out all users under 18? Seems simple enough to me.
But then again, this is why I don't go on MMOs. If me and my freinds wanted to have a nudist stripper party, we'd have a nudist stripper party - no kids allowed. "God" or something isn't going to come down from the sky and shut the thing down.
Why can't MMOs be more libertarian? You create the world, let the players control the history. Who gives a shit what they do with it? As a matter of fact, the only thing Blizzard should be doing here is patrolling for illegal downloaders who walking into the World without paying. Beyond that, let them do what they want. If they hack the game to have a bazooka, yet them have a bazooka. Let things unfold as they will.