[JohnBooty]

I'll drink to that!

As somebody who's organized community gatherings himself (and made plenty of mistakes in this area himself) I do feel that organizers play an important role as you say.

To put it in really literal terms, when I organized my first meetup, we had a mix of under- and over-21 members. I was really concerned about underage drinking. I really strongly let our members know what was expected of them. I think I stopped just shy of threatening to beat them up and/or report them to the FBI if I caught one whiff of something bad happening to anybody, especially the underage members. I definitely got the message across, at least.

While that kind of approach obviously doesn't directly scale/translate to a professional conference, I think the overarching principle is the same. The organizers set the tone, outline accountability, and (if it's a multi-year event) weed out repeat offenders. The rest is up to the community.