I once had a Spain bidder who intentionally OVERbidded my item and planned to win it 100%. Since my card was just $5 and it was overbidded to $20, I didn't bother to ship with tracking (which costed $15 for me).

1 month later, he filed a claim that I didn't mail him anything. Notice: he DIDN'T response to my email, no message went back to him. And this buyer has 850+ rating in ebay.. lol

To me, some people just planned to do that whole thing from the start. OVERBID an item (like put 10K bid for Durant Exquisite RC /99), then file a claim that "card is missing", "card is not described" "empty letter".