there are several tricks that are used on Ebay quite often that are hard to pin on a person. One common trick that is used to find what your high bid is (if you are high bidder) consists of the scammer gradually increasing his bid until he becomes the high bidder...he has now found your high bid. Then, he cancels his bid, claiming it was a typo. Then, he can wait until the end of the auction and enter his winning bid. I have bid against scammers that had 75+ cancelled bids in the last six months, all supposedly typos.

Another scam is to shill bid by either setting up another account (easier to catch because the source computer is the same as the listing computer) OR have a buddy bid from another computer. If it works by driving up the bid amount, they gain. If they accidently are the high bidder, the seller delists the item at the last minute OR sometimes he eats the Ebay fees.... for small items, the fees are small so it is no big deal. For cars, they claim a local sale and delist early.

Also, there is the feedback scam where the scammer buys a bunch of small, cheap items, pays quickly and gets great feedback. Then, he sells something of high value. Many bidders check his feedback but miss the point that the feedback was from buying, not selling.

I have sent evidence of scamming to Ebay but they always respond that they investigated but found no fraud.