"Hi, I'm so-and-so, sign up for my affiliate program!"
"If I promote your program, will you promote mine?"
"No, we don't promote anyone else's websites but our own."
"If I sign up for your program, can you at least link back to my site?"
"No, we don't link back unless you buy banners."

End of conversation - trip wasted.

That's really the problem. You really have to "work" people a bit at shows. Usually the last day is when I get most of my business done. It usually goes like this,

"Had a really great time over dinner the other night. I will start sending you traffic when I get back to Boston. Heard your traffic is some of the best in the biz..." Deal for traffic gets made.