As the biggest social network across the Internet, Facebook has a lot of people to reach. And the current usage evidence shows that people really want to let their friends what’s going on even when they’re not near a computer—so that means mobile devices. The result: Facebook has plans for its own smartphones in the works. We don’t know yet if the handsets themselves will carry Facebook branding.

The interesting angle here is that the carrier is rumored to be AT&T. The source of the information declined to substantiate that because the telecommunications giant hasn’t yet made a solid deal on the prospect. This article at Bloomberg outlines many of the features and elements expected for the smartphone,

“People are increasingly updating their status when they’re on the go,” said Augie Ray, an analyst at Forrester Research Inc. in San Francisco. “Facebook is a very popular application on every single smartphone in the country.”

The new phones are slated to run Google Inc.’s Android operating system and will probably carry the AT&T brand in the U.S., according to one of the people. Facebook hasn’t decided whether its name will be used on the devices, the person said.

The social networking company is working with INQ Mobile Ltd. on two smartphones—one which will have a pop-out Qwerty-style keyboard and the other sporting only a touchscreen like an iPhone. Using Android as their base operating system will likely make it every easy for them to develop both phones simultaneously with the same software, look and feel—plus, it will give Google yet another bit of a stake in the social networking fishbowl as they’ve continued to make their presence known there.

Although the handsets will be designed for Facebook, they will also offer access to other social networks.

Facebook hasn’t yet monetized its mobile apps but with this project it looks like they might start working towards putting advertisements into them. Unlike other advertising networks, Facebook uses its internal mechanisms to produce social-advertising that acts pretty much in the same manner as getting messages from friends (in fact, most advertisements in the social community are generated by friends Like-ing an ad.) This is a good time for them to do this, as the introduction of a branded phone will greatly increase their reach in the mobile landscape.

AT&T’s stake in this is also interesting as the telecomm company appears to be trying to retain as much of the mobile market as it can. They’ve also been working with Nokia on a massive mobile app contest that’s calling for developers to swell their app ecology—adding INQ and Facebook’s phone to their dockets will prevent them from slipping in the face of their competitors when it comes to handsets.