If you're selling on eBay and something goes wrong (buyer claims she received a box of rocks), there really isn't much to do. PayPal and eBay favor buyers so much that if the buyer really wants her money back, she'll certainly get it.
That doesn't sound right. I bought a mobile phone on eBay and the seller sent me a unit that was (a) a different model and (b) clearly used. I jumped through all kinds of hoops, culminating in a letter from my lawyer certifying I received a different phone. The end result was, I could not return or exchange the unit, and my negative feedback and rating were erased. Stories like mine are legion. eBay emphatically does not favor buyers, they screw everyone equally.
Because nefarious sellers and buyers would have unlimited license to prevent negative feedback from being posted to their account, ever. They would always appear to be a new seller/buyer.
Hilariously, sellers can't leave negative feedback for buyers: http://pages.ebay.com/services/forum/sellerprotection.html
If you're selling on eBay and something goes wrong (buyer claims she received a box of rocks), there really isn't much to do. PayPal and eBay favor buyers so much that if the buyer really wants her money back, she'll certainly get it.