ebay does not guarantee the reliability of the seller (or buyer for that matter). i have bought and sold a number of professional cameras on ebay. here are my observations-
1. only buy using paypal, since they control the money that is exchanged, they have a lot of leverage over a seller that does not satisfy the customer. if the seller using paypal is a fraud, paypal will refund your money. 2. check out the reputation carefully, sellers that also have a regular established business is a good sign. feedback ratings are a clue to buyer satisfaction. see what else they are selling, scammers usually have a number of "too good to be true" auctions going at the same time. 3. read the description carefully and pictures (if not generics). anything not mentioned figure you don't get. instructions, warrantee, lenses, batteries, chargers, memory cards, are a few items that might not be included. is it really a new, never before sold item or is it a returned or refurbished item. if you are uncertain on any point, email the seller. If the seller does not respond then they are not anxious to sell which is not a good sign for a buyer.