Brewers travel from all over the country (and the world) to attend the festival and promote their craft. But as many, many brewers have expressed to me, both this weekend and at past festivals, they don’t really want to spend a lot of time on the festival floor because it tends to devolve into a semi-drunken shit show, especially at the weekend evening sessions. Seasoned festival veterans long for the brief moments in between the raucous screams that accompany the near-constant dropping of glasses (many of which are now done on purpose). Many brewers simply don’t bother to attend the sessions because they have no role to play and the scene isn’t about their talents and what they do for a living.That's the GABF, though Oregonians are forgiven for mistaking it for the OBF. That's Andy Crouch, who has a quite a long and interesting post on the fest.
Relatedly, Doc Wort suggests the GABF travel to different cities every year, a proposal I heartily endorse. That would really undermine the frat-party quality, because you'd have a new crowd every year--one comprised mainly of first-timers. It would also do a lot to advance the stated goal of the Brewers Association--to educate Americans about craft beer. It would be logistically more difficult, but it seems like an industry of this size could manage to pull it off.
Update: Brewpublic offers the local perspective.