Facebook is testing the placement of a second web search box at the top of its site, All Facebook reports. Whether it will be a permanent addition is unclear – also how many users will receive the beta is uncertain as well. If it were to become a permanent fixture, however, it would give the search engine in question – most likely Bing-powered web results, All Facebook says - a powerful boost given Facebook’s 250 million daily users and 600 million user base.

Such a move makes sense, All Facebook speculates: Facebook would receive a considerable revenue from Microsoft for the placement, comparable if not more to the hundreds of millions Google paid MySpace a few years ago.

Also the move would be welcome to investors as Facebook moves to launch its widely expected IPO.

Mobile Boost Too

Bing also enhanced its mobile search functionality, the company said in a separate announcement. It has updated Bing for Mobile browse to make it easier for faster image search, real-time transit and directions and app search for the iPhone.

Bing Grows Marketshare

Of the two moves, the Facebook tie up is clearly the most significant. Even without it, though, Bing has been developing momentum in its competition with Google. Microsoft Sites, mostly representing the Bing search engine, reported 13% growth in US explicit core search queries between December 2010 and January 2011, according to comScore qSearch data. (via Marketing Charts).

Microsoft’s explicit core search queries rose from about 1.97 billion to about 2.22 billion. Nearly 17 billion explicit core searches were conducted in January 2011, up 3% from about 16.4 billion in December 2010.