Slate has an easy-to-follow article about the study of eBay auctions by economists.  An excerpt, with a link:

Are eBay auctions rational or irrational? - By Tim Harford - Slate Magazine
Auction theory offers an argument that a secret reserve price is better. A secret reserve price allows bidders to see each other’s gradually ascending bids and thus draw confidence that they are not alone in prizing the item. Even though the bids are too low to beat the reserve, they serve an important purpose of reassuring bidders that others are also interested. An open reserve price on eBay makes that reassurance impossible; nobody can submit a bid below the open reserve, and lacking any signs of confidence from other bidders, nobody may submit a bid above it either.

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