I have sold a few frames and misc. parts and my experience has always been pretty good. One time a guy in Australia bid on a frame and won it, despite the fact that I said I'd ship to the continental US only. I didn't send it to him.

Recently I sold a crank set and the buyer asked if I had the spindle. I said yes and told him how much more I wanted and he got a bit irritated-he wanted it free since it was of "no use to me". He ultimately did pay and that was the last I heard of him. No feedback despite the fact I was a nice guy and gave him a positive.

No good deed goes unpunished.