I never participate in the fat quarter swaps because of the postage. What is the point of giving one fat quarter and getting one. I would rather pick out my own at the LQS. When I used to do this, I would give a LQS piece and get a Joann fabric one.
I have participated and enjoyed the fat quarter raffles. Every one sent in 2 FQ with a theme named by the hostess, one was kept by the hostess and the other went into the prize. A name was drawn and winner took all. No different than purchasing a raffle ticket, you dont expect to win. Then the winner hosts the next drawing and can name the theme of the raffle. So the winner actually gets two piles of FQ.
We have done this with my on-line quilt guild where we had a set number of members. Nobody got burned because we knew each other.