I've been a regular ebay shopper for a long time, not as bad as Keoke but pretty bad. There's a zen to ebay, in language, presentation, feedback, the whole shooting match. Once you've got the feel, you can smell the scams right away. You can also feel the reserves, and you can give a pretty good estimate of who your competition is and how they bid. There are lots of tricks to it to win, and plenty of clues when there are problems.
The easiest thing to do to test a listing to see if it's legit is to ask for a photo of something not on the listing. Any legit seller will happily do it. If they refuse or make excuses, you have your answer. Excuses and explanations are always a dead giveaway that there are problems, because legit sellers WANT to sell, and try to accomodate. There's a pretty long list of obvious signs of scams, but anyone seriously interested in buying on ebay needs to spend some time there, get the feel of the joint, before buying or there's a good chance you'll get burned. But once you spend that time, you can get amazing things at amazing prices and you'll be hooked.