I disagree with you Paul. I understand about retribution or reciprocity or whatever you want to call it, but the reason there is negative feedback is just for this. The guy sold a chip he didn't have. Brian needs to get his money back, leave the negative feedback and get some sleep.

If Brian is a buyer more than seller, then the feedback doesn't mean a whole lot. But he also has the opportunity to write a rebuttal in the feedback. Its hard to argue with "sent the money, but seller claimed he had no chip to deliver".