Picking up on the thought about a threat to Ebay's business model, there is one here. If AS worked slightly differently, it could cut down on Ebay revenue.
Scenario:
Current high bid: $2.00
AS user A bid: $15.00
AS user B bid: $16.00
AS user C bid: $17.00
If AS sends all those bids in, C will win for $16.50. But AS could look at these and say, "C is going to win anyway, so I'll only submit the C bid." Then C wins for $2.25.
As an Ebay user since 98 who bought stock when I saw the unbeatable business model, I usually take the company line. But I recently sold the stock, and I've spotted a few potential holes. This is one of them.