Why sell you hard earned bitcoins on ebay?
A lot of Bitcoins are sold on ebay at a premium, and the seller most likely will use the sale to buy more Bitcoins than he had before the sale (because the seller has a MtGox exchange account or similar). Even though this seems like the buyer is being scammed, this is not the case. The benefit to the buyer is that they don't have to verify and go through a exchange.
However, I would advise against selling Bitcoins like this mainly because of the chance that the buyer will charge-back or something similar after you transfer a Bitcoin that can never be returned.