There is starting to be credible evidence that Ebay and Yahoo may eventually join forces to fight Google. Last week AOL accidentally dumped millions of lines of search data, this data was quickly combed over by SEO firms like VKI Studios. We found some pretty interesting information. Namely it looks like Google has a 60% strangle hold on the search market. Obviously Yahoo and Ebay know this.
While most companies have been trying to partner with Google, Ebay has done the opposite. In fact they have gone as far as banning Google checkout as a payment option on their site. And a couple of weeks before that they did a long term deal with Yahoo.
Ebay is one of Google's largest customers (if not their biggest); they understand the power of search, and the power of Google. This is just my two cents but I have a strong feeling that Yahoo and Ebay may join forces in the next couple of years to try and turn the Google tide.