[aelhaji]

Let's say that the first bidder placed as a proxy bid $100 but eBay only shows $1. This will already exclude everyone who has a maximum-willingness-to-pay lower than or equal to $1. A second bidder might put as a proxy bid $120. This wil result in eBay setting the highest bid at $101. At that price nobody with a maximum willingness-to-pay lower than or equal to $101 will reveal their max. The Vickrey auction doesn't reveal anyone's bid and, thus, you collect a lot more bids (demand curve data). I agree with you, however, that the eBay mechanism results in the same person winning the auction.