If your shopping from Ebay, once you find the item. ALWAYS look at the dealers profile. See what his feedback is, and how much he usually sells. 90% of Ebay is normal people selling something for variant reasons. But people do run business from Ebay, so some items are legitimate. Ebay is the place that you simply have to know how to shop.
If the dealer dont really sell anything, or has no profile. Then its considered a risk. Personally i dont buy any kind of computer hardware from Ebay. Because once your stuck with something thats not what you wanted, or if its DOA. What can you really do...? If you do manage to get your money back, how much trouble and time would it of took...? Well, plunty.. Overall its more of a risk. Just make sure you know how to shop there.