Avatar trading will work a bit different than item trading. So users can trade avatars to other users, and the other user will accept, then the original user must accept again. During this process each player may offer up items, gold, and other avatars to barter.
The reason for this two step process is to make sure that the other player is offering up their fair share as well. Kind of like a bartering system, but with avatars. I guess the bartering system doesn't have to be limited for avatars, but any items/gold/avatars. Hmmm, I'll think more about that later.
I think avatars will be a bit more popular once they start appearing everywhere.