If you can’t beat ‘em, join ‘em. Sources close to the Windows Live and Bing divisions at Microsoft claim that the company is developing iPhone applications for their respective products.

Neowin.net is reporting that both Bing and Windows Live Messenger could soon make their debut on the iPhone, presumably alongside the forthcoming Windows Live Wave 4 updates coming around March, 2010.

For their part, the Windows Live team appears to be working aggressively to move its applications to the iPhone, and only last week Microsoft principal group program manager David Raissipour confirmed to Cnet News that “We are actively working on it” when asked about rumors that a Bing app was in the works.

Of course, Microsoft is no stranger to the App Store, having previously released the Microsoft Tag and Seadragon Mobile apps last December. It’s clear that Microsoft intends to go multi-platform in order to grow its market share with its web and cloud applications, and the iPhone is clearly too large to ignore any longer.

Hammering home that point, Neowin did an informal poll of 1,300 members and found that 29% of them owned an iPhone.