I have been having this debate with a few people offline about the value of being at Expos, specifically in a booth.
When you have a tangible offering (especially commodities and hardware), having a booth -- and doing it right -- can pay off. At the very least, it is a branding opportunity. And for some sectors, like VoIP, it means that you at least have the cash to buy a booth and maybe more than a short-term arbitrage player.
The problem with my 2 specialties - consulting and training - is that most companies do not think they need either one. So no booth space no matter how unique is going to get over THAT misconception.
Then there's the fact that both consulting and training are customized per project. There is no one size fits all. There is also a boatload of politics involved in the hiring for consulting and training (and bruised egos to go with that). This can not be alleviated in a 3 minute window at a booth. I can get leads, but I also know all the companies and could use the booth and travel costs to mount a marketing campaign that would be just as effective.
The issue at many Expos (conferences) is that executives are there to party and measure up. How well are they doing compared to their "peers". In that environment, it is difficult to tell someone who doesn't measure up that he needs to hire a consultant.
Not just because I write for them, but TMC's ITEXPO is one of the events where people show up to buy or get specific answers. How many folks show up with a list of questions that they need answers to? Answer: very few. Rich Bader from EasyStreet used to do that at ISPCON shows.
So why do you go to expos? (Or why don't you go?)