I like this and would participate. I think one thing that really helps with this site in making this possible is the chat feature. I wish we could get some sort of a better education on how to use it (for example, the chatrooms show up on one computer, but my laptop, they don't (the bar shows up for them and I can click chatrooms, but there is nothing listed there, where as on my desktop, there are always 4 or 5 rooms listed).
There could be a master folder, say "trade night 1/15 8pm-10pm", and in it, each of the "dealers" could have a thread, say "Bill Menard's Table" and in the thread you can post pics of the cards that are available and asking prices. Be great if they could somehow be sorted, like by sport and then by team or by year or brand or something along those lines. Then, if you like something at someones table, you could hit the chat button for that person and talk with them about a deal. Paypal or trade could be arranged and then executed.
One issue I will have is trading with people I don't know or don't have a solid rep here. I'd be a bit worried about getting scammed, especially if people found out about this "show" and starting coming to this site specifically to try and swindle. I can see it happening very easily. That is about the only negative I can see. With the chat feature, it should go very quickly as far as making deals. Hell, I'll even fire up the paypal on another window so that I can print and pack in real time and mail out the very next morning. This way the buyer gets their item as fast as possible.