I think you need to be a little less general here. Granted there are some rogue traders out there who sell faulty goods and don't offer refunds, but for every one dodgy one there are a thousand that are excellent, selling great quality items for a very fair price.
None of this is a function of Ebay. Ebay just makes the world of commerce more accessible to joe public, so anyone can create an Ebay shop whereas they may not want to set up a formal trading facility.
I have recently bought from MPL tuningparts and Ricambi Weisse, both from Germany, both on Ebay, both provided excellent goods at a fair price.
In hundreds of Ebay transactions I have only had a disagreement with the other party on three occasions. I'd call that at a successful result.
Mark.