I'm sure we've all been there - you buy something on eBay or from a third party on Amazon, and what you get is either rubbish or not what you asked for. The correct thing to do is to talk to the seller first to try and resolve your problem, and then when everything is said and done, leave feedback rating the overall experience. Several times in the last year I have gone through this process and ended up feeling the need to leave negative feedback. The most obvious case was some bluetooth headphones I'd bought from an eBay seller in China that were so obviously fake that it was hilarious he was even trying to convince me I was doing something wrong. In each of these cases, I have been contacted shortly after the negative feedback to ask if I will remove the feedback in return for a full/partial refund. This has tickled the curious side of my brain into wanting to know what the value of negative feedback is. The obvious way to find out would be to buy items of various different price and then leave negative feedback and see how far the sellers are prepared to go to preserve their reputations. The obvious problem here is that this would be an unethical and unfair way to do science. Perhaps it would be possible to crowd-source anecdotes until they count as data?