This looks like a fun thread. I'm sure everyone wants to hear my neg. feedback story:

(1) The only time I ever left negative feedback was when I won something on Yahoo! (a place I stopped going to by the way; I only seem to have time for eBay). Anyway, I won something on Yahoo from a woman who had about 8 positive feedbacks and 4 negatives, mostly for not replying to e-mail regarding completed auctions. She never replied to me either, so after two weeks, I left neg. feedback. Then about two weeks later she e-mailed me to complain and say her house had burned down and that she had more important things to do. (I don't believe her.)

(2) MY SUGGESTION is to almost always not leave negative feedback (because of retaliation). Rather, inform eBay and ask for a credit against eBay fees if you are not paid for an item, for example. I think after 3 such complaints/credits, eBay will take action against the offender.

Robert