Seth Godin has a post on his blog about building better hallways to build communities among "tribes" of individuals with common interests.
What would happen if trade shows devoted half a day to 'projects'? Put multi-disciplinary teams of ten people together and give them three hours to create something of value. The esprit de corps created by a bunch of strangers under time pressure in a public competition would last for decades. The community is worth more than the project.
He's absolutely right. Many trade shows include a social activity or competition (the iMedia Summits are great for this) that put small groups of attendees together for activities like sailing or skiing or mountain biking, affording everyone the opportunity to get to know each other better, and knit the community together with shared experiences.