I've never actually bought anything on ebay....
But I've known two people who've gotten scammed.
one of my sister's ordered a tiffany's bracelet....turns out it was a fake.
and then my boyfriend's roommate ordered a laptop - laptop never came, turns out the whole thing was a scam. luckily, he was just able to charge back the charges on his credit card, so he wasn't out any money. they were able to find the guy, so he now has to make a statement to help get the guy in trouble.
boyfriend's also sold a few things on ebay, including a psp, ps2, and other video game thing.