The mobile search wars continue, and Google just won an important tactical victory over rival Yahoo. Opera, maker of mobile Web browsers, has switched its default search from Yahoo to Google.

Opera's numbers ain't too shabby. More than 35 million people have actively pursued and downloaded Opera Mini to their mobile phones to improve their mobile Web experience. Opera Mobile has shipped on more than 100 million phones. According to Opera, these consumers tend to use the mobile Web more frequently and actively than consumers with more static, less dynamic mobile Web browsers. For Opera to switch up mobile search providers from Yahoo to Google is yet another blow to Yahoo's mobile efforts. That's 135 million fewer people who will be using Yahoo.

Opera's desktop browser has used Google search as the default option for seven years. "Google and Opera have established a valuable relationship over the years and we look forward to continued collaboration on mobile products," said Jon von Tetzchner, Opera CEO, in a prepared statement. "With 2008 poised to be the year the mobile Web goes mainstream, Google and Opera are extending this collaboration to give our users immediate access to the quality and convenience of Google's search results. We're excited to extend this productive relationship and we hope that the nearly 100 million people using our mobile products will agree."

The new search functionality will be available beginning Saturday, March 1. For the next few days, at least, Opera's browsers will continue to use Yahoo search.

The timing is certainly interesting. You have to wonder if Opera is ditching Yahoo because it would rather not be associated, even indirectly, with Microsoft. Microsoft's Internet Explorer is, of course, a direct competitor to the Opera browser.