Well... I participated in the Piggy Swap last year (for the first time) and I don't know if anyone had an issue with that. All I can say for sure is that I have more seed than I need right now and am hoping to give it away (and resist asking for any - well, better make that many - seeds).
I don't think you can really go into a group swap with the expectation of getting an "even" trade, but I could be wrong about that. I would say that I think if you are offering 50 packets and they are all requested, then yes, you are obligated to send them out.
