bill on ebay, you can't be held liable, thats why you should use paypal for all credit card transactions, they have a policy, of taking the loss if they do a chargeback.? and also if you accept check as payment wait for the check to clear before you send the item.? after the check clears it is final.? but if they cancel the check and you send the shit before you get the check or if it bounces, you're fucked
Taken from the ebay site:
eBay cannot force a seller to honor their transactions. You should leave appropriate feedback for the reluctant seller to warn other buyers of his or her past history.
Depending on your local jurisdiction, you may have independent legal recourse against the seller. They also refer you to a site that handles cases of bidders committing fraud and so on.