The only swaps I have participated in are on this board. Both have been good experiences. I think part of the reason for this is the attitude of encouragement I find here. We all applaud the work of others, and try to encourage attempts at new techniques, etc. True, some prewash and some don't, so that might be a deterent, but in general, swaps can be a good sharing/learning experience.
I'm sorry others have not had as good an experience with swaps.