As an aside, I find it gives me a great deal of satisfaction to sell privately, as it always seems as if the stuff's going to a good home etc.
But I've found when I have tried selling stuff on Amibench, fo example, there are some right cretins on there, who will try and browbeat you into selling stuff for next to nothing, or even be downright abusive (there was some guy called haemarrhoid or something that I particularly remember). Has anyone else encountered this?