I did something pretty stupid on eBay once. I sold one of my R/C cars for $500 and had it all boxed up and ready to go by the front door of my apt. The only thing I had to do was wait for Paypal to confirm payment and send it to the postoffice. Well, my roommate, being the nice guy he is, sent the box for me while I was at work. I come home to find the box gone and the seller writing to me saying he wanted to retract his bid because he thought he bid more than he could pay.
So I was out a car, money and had no one to be upset with.