I don't come to these things for the social aspect, so I'm probably not really the target audience, but...
What if they took the focus away from the frags? Still load up their tanks, keep the sales and promos, bring in food if they want, but just have people come hang out... talk about fish or corals, test Bob's latin, whatever. Maybe have a guest speaker or setup some crazy exhibit tank (obviously cost would/could be an issue), etc.
If people want to swap frags, then let them setup the typical buy/sell thread here and do that on their own... ABC doesn't have to facilitate it, though.
I dunno... just trying to think outside the box a bit. I'd much rather have someone talk for 45 minutes on the basics of water chemistry than to wade through portable frag tank after portable frag tank, each of which looks better and has nicer corals than my display tank has, and none of which I can afford.