Okay, I can see the pros and cons of both Dave's and DogNDaylily's ideas.
If everyone just throws their seed into one big pot then you run the risk of people giving a little but getting a lot. Or giving "not so good seed" but getting lots of "fancy, expensive" seed in return. But everyone gets a good shot at getting seed they want.
On the other side, if everyone ends up doing mutual trades you could end up with a situation where very few people get the seeds they want because only one person in each trade has something the other wants. You would have to hope people would be very generous with "freebies". But if you could make the trade each party would be highly satisfied with the outcome and it would be harder for someone to "game" the system.
Seems to me there has to be a middle ground that would increase the chances of getting the seed you want but not being a complete free-for-all where some people end up feeling like they got a raw deal.
Any thoughts??