"The seller puts out a "buy it now" at too good a price to be true. It is immediately snatched up. To ensure that the transaction does not get reversed, he actually sends a letter to a random location in the same zip code (doesn't do this within Ebay so no way to confirm tracking number goes to the buyer's address). This provides him with delivery confirmation.

So eventually the buyer opens a case. The seller can then produce the tracking number that shows that something was delivered to that zip code. EBay closes the case because the seller has a delivery confirmation and the buyer is screwed out of his money."

-From a eBay forum post.