An online swap box would be awesome, but as you said, AB, it can go really great or really badly. I'd have to think a bit about how to do that fairly, but thanks for the idea!
Maybe the online one would be best to randomize who gets what. Like uhhhh... everyone puts in a dress that is at least knee-length, then we assign the different dresses numbers and run them through a randomizer, match them up with everyone's random ID # we create for this or something... And all the dresses are sent to the host, who re-distributes accordingly. Or we can do all the show-off of the outfits online and then exchange addresses when the randomizer gets finished. *shrugs*
I'm liking the online idea but it requires all participants to take pictures and agree to certain standards for the swap.
Hmmmm... think think think... *Winnie-the-Pooh thinking face*