There are things I never buy from eBay. Always look at the seller information, how long they've been in business, are they shipping from China, their feedback score. I've generally had good luck, and run across a couple of dishonest sellers (like the rug I bought that was interestingly crumpled in the photo - upon opening the box there was a large chunk torn out of it that wasn't mentioned in the ad!)

The same kinds of practices are moving over to Amazon, so if you buy there and it's a third-party seller, look at their feedback.