Senh: Google did get their start with Yahoo when the web directory used it as their third-party search engine. Yahoo is mainly a content company nowadays, but they're still the second largest search engine in the search market. Owning Yahoo and replacing Bing, which Yahoo currently uses for search, with their own search engine would make Google even more dominant in search. It's insurance against Bing (Microsoft). Expect a bidding war between Google and Microsoft.