Microsoft’s Senior Product Manager Greg Sullivan said in an interview, talking about Bing, that “the search engine has been heavily integrated into the OS, so it would be hard to offer an alternative”. Even though other search engines would be allowed to create a downloadable app or even hub, no other company would be allowed to take the place of Bing as a default Windows Phone 7 search.
Google has launched its initial release of the Google Search app for Windows Phone 7, allowing you to search the web, images, local, news, and more. The app also supports Instant Search with suggestions appearing automatically as you type. The initial release is available for free in the Marketplace by looking for “Google Search”.