I've written before that Yahoo has their fingers in so many pies that they don't have necessary attention on search that Google does. Google only buys companies that offer services, software and add-ons which increase value of Google search experience. http://www.website101.com/arch/archive140.html
Yahoo buys companies when they think they might be able to squeeze some extra bit of profit from them and add to already confusing array of services which take an alphabet soup of 109 Yahoo "properties", broken down alphabetically. http://docs.yahoo.com/docs/family/more/
Yahoo bought up all available search "properties" within last couple of years and, as I said in mid-July of 2003, "Well if it is a horse race, Yahoo may gain on leader Google if they are able to integrate their Inktomi and Overture (and by extension, Altavista and Fast/AllTheWeb) purchases into relevant search results that searchers trust. But all of Jockeys on those horses will be whipping their charges toward finish line with an eye to winning purse." http://searchengineoptimism.com/Yahoo_acquire_Overture.html
The fact is - Yahoo search is no better than Google now that they have bought up all real competitors. Referred traffic from Yahoo search results to web sites is still only one fifth that of Google at 70% versus Yahoo's anemic 15 to 20%. http://searchengineoptimism.com/Google_refers_70_percent.html
The new MSN search may pose a threat to Google if they continue on their current path toward relevant search results. As of October 2004, Google market capitalization of $52 billion with shares hovering around $160 per share price, reflects true value of Google.
Yahoo is kind of like a WalMart, a "Portal" with everything under one roof and over a hundred wildly diverse "properties" that don't contribute to search relevance or search value. Google confirmed today that they have no intention of becoming a portal, but instead intend to keep laser focus on search that made them number one. This focus was underlined by CEO Eric Schmidt's comment in Financial Times of London, "We are not building a browser," to stop that circulating rumor. (Financial Times)