A Cre8asite thread named Google threat to eBay discusses an article which was recently published at Yeald.com named eBay snipered by Google-Amazon comparison shopping threat.
The real reason [that eBay wants to restrict Adwords customers from purchasing the eBay trademark] appears to be that Google matches ads with listings generated by relevant keywords. This makes it possible for searchers looking for a specific product to compare prices on eBay with prices elsewhere on the Web. It also significantly extends the reach and potential of merchants to sell their goods well beyond the relatively limited confines of the eBay marketplace.
Bill Slawski, forum administrator, makes excellent points about the article. Besides for some of the deeper ideas by Bill, "I do find it pretty odd that this article doesn't mention Froogle" Bill says.