I could understand if a person got a bad deal at a local store, he might not want to shop there again. BUT if that person said nothing to the owner about the problem and gave him no chance to resolve it, that's just spite and ignorance.
To go on ebay, and have a bad experience once, and judge 20 million other members by that experience, makes no sense. For every bad experience, how many great ones are there? What do you lose by not interacting with those other 20 million people, who might have something you want? (I paid $75.00 for a Starrett digital height gauge in a wooden box, barely used,on ebay. The book price was $300+. Would I have lost that deal?)
To put it another way: If you got a bad piece of meat in an A&P supermarket in Des Moines, and moved to Omaha 3 years later and lived across the street from an A&P, would you not shop there because of your past experience in Des Moines?
Let's reduce it to the rediculous a little more: If you got a bad piece of meat, would you stop eating meat?
If you are thinking that answering YES to both of these examples would be foolish, then you are getting my point about some peoples attitudes about ebay.