No, Facebook isn't building its own phone. But UK mobile service provider 3 is launching a mobile phone whose primary function, besides making phone calls, is social networking.
The phone is called INQ1. Its specifications? Fairly standard: a 2.2 inch QVGA screen, 3.2 megapixel camera, HSDPA, accelerometer, 50MB + 4 GB of memory. The platform that powers it was created by INQ Mobile, a company that's specialized in mobile social networking solutions.
The phone is not available yet; the details are sketchy; I was unable to find out what platform it's really based on (I assume that INQ's software will work on top of an existing platform such as Symbian of Windows Mobile) it's based on Qualcomm’s 6260 chipset and uses the Brew OS. What's important is that INQ1 will provide quick access to Skype, Facebook, Windows Live Messenger and Last.fm, with eBay support coming soon.
This is all UK only, where INQ1 will be available for as low as £15 per month offering unlimited free Facebook, Skype, Windows Live Messenger and web access, as well as 75 minutes of calls to other networks, unlimited texts, unlimited email and unlimited free 3-to-3 calls.