Lots of folks show up again at Seattle's Green Festival, despite a seemingly "down" economy. Could it be that sustainability helps business keep an even keel despite fluctuations in the stock market? Methinks so.
Regarding "getting customers" at trade shows: I don't subscribe to the idea. It's too stressful to think in those terms for me. I like "make relationships". This opens it all up, and lets you think about every single person you see as a relationship, from the folks that clean the floors of "soy-product" when we've all packed up, to the people who sign up for our services.
Just connect to people and have fun. Let that be the purpose of the trade show and do the business-y stuff another day. ( That is, unless, you really do get lots of real work from the shows due to your particular revenue model. For the business-to-business folks who specifically cater to the trade show folks, it's all nitty gritty business all day, and the "relationship building + fun" stuff might not be your best bet. Try it toward the end of the day after you've done all the heavy lifting...)