Facebook has earned the allegiance of Taiwanese manufacturer HTC to build a smartphone fully integrated with Facebook services.

The device has been given the codename “Buffy” and is reported to run a modified version of Android with services from Facebook deeply integrated in its system. According to AllThingsD sources who have insider information about the project, it will also run HTML5 as a platform for its applications.

Speaking to AllThingsD, a spokesman from Facebook declined to comment about Buffy. So did HTC.

But, the Facebook representative did say that the company thinks that every mobile device will do well when it is socially integrated. Facebook is also working across the entire mobile industry to bring “powerful social experiences to more people around the world.”

Targeting the mobile industry is an essential key for Facebook’s success in the future. Facebook claims it has 350 million mobile users and has partnered with 475 global mobile operators.

The Buffy project is a significant catalyst for Facebook to produce more socially-centered mobile phones, together with the help from phone manufacturers like HTC.

HTC is one of the companies that built mobile phones with a dedicated Facebook button, such as the HTC Salsa and HTC ChaCha. Inq Mobile and Motorola also developed phones with dedicated Facebook buttons.

With the source code of Android 4.0 Ice Cream Sandwich released, there is no certainty on how Facebook will weave the code into the device. The device may have a full-touchscreen with the Facebook button integrated in the OS–just like the virtual buttons in the Samsung Galaxy Nexus. Or, it could still sport a QWERTY keyboard just like some existing smartphones with dedicated Facebook buttons.

What do you think of a mobile phone fully integrated with Facebook?