Facebook has announced the acquisition of Face.com, the face recognition start-up based in Israel, for $100 million. Why the social network giant has acquired the company is not known, but here are some possible reasons.

Improved Tagging

The most obvious reason is to improve the company's tagging feature, which currently allows users to type in a friend's name and assign it to a person or object in a photo. It's long-winded, so Face.com could associate a face with the photo automatically and assign the name. This could also integrate into the mobile apps, particularly the recently launched Camera+ app, which exclusively shows photos. It could be as simple as taking a photo, hitting the tag button and holding the camera to the face.

That would also be useful for tagging while travelling, where people can be assigned in a photo through one click or through a list of suggested names.

Facebook Phone

It's been consistently rumored, so perhaps there is some legitimacy in the Facebook smartphone stories. Obviously such a device would have direct integration into the social network, and Face.com could be used as a cornerstone of the device. The Galaxy Nexus supports facial unlocking, but was met with controversy over security concerns. Offering Face.com's technology in the camera app on such a phone would be an advantage over Apple, Google and Twitter.

Instagram Integration

Facebook acquired Instagram for $1 billion, so the $100 million reportedly splashed out on Face.com is a small outlay in comparison. Integrating facial recognition technology into the popular photo editing service, and then uploading those photos with the tags, would bring added convenience rather than doing the two tasks separately. If identities were remembered for automatic tags, then the process would be simplified further.

Third-Party Face.com Support

On the blog post announcing the deal, Face.com said it loves the third-party developers and plans to "continue to support our developer community." Integrating the technology into third-party apps, while supporting Facebook, would extend the reach of the technology and Facebook beyond the Web site.

TechCrunch's sources heard the deal is worth around $80-$100 million, while AllThingsD's sources claim the actual valuation of the company is between $55-$60 million in cash and stock.