I'm pretty sure that once you leave positive feedback as a seller, you can't then report the buyer at a later date.
So if they decide to try and rip you off, you can't then report them and give them a mark on their account. For that reason alone I never leave feedback for buyers until they receive the card
PC: Carolina Panthers and University of Arizona players, especially in UofA uniform
Stewart PC: http://s1158.photobucket.com/albums/p615/ZonaCats8/Jonathan%20Stewart%20PC/?start=all