In April 2010, NPR aired a program about a curious case of a Florida man who purchased a $44 item on eBay, left a negative feedback, and got sued by the seller.
Just a few days ago a local Florida newspaper reported a similar story where another Floriday man got sued for leaving a negative feedback after attempting to buy a $6 luggage tag from a seller in Boston.
The funny/sad thing is that this article mentions the case from April 2010 as well:
Mike Steadman was sued by a Miami man who claimed Steadman’s negative feedback ruined the seller's reputation. But Steadman said the clock he bought arrived broken, and the seller wouldn’t replace it.
Steadman thought the lawsuit was frivolous, but three years later, his attorney is now preparing for trial, ready to argue the sellers agreed to accept feedback, which is how eBay works.
I guess the takeaway from this story is this: if you leave negative feedback on eBay then be prepared to fight it in court.
The NPR story from 2010: