Facebook has acquired Face.com, the facial recognition software company whose products power Facebook's photo tagging suggestions, according to a blog post.

Rumors of the acquisition began to circulate in late May.

Face.com also provides branded Facebook apps. Photo Tagger is very similar to the native Facebook app, while Photo Finder, the company's first app, helps users find untagged photos of themselves. Face.com offers an API (application programming interface) that powers third-party apps including CelebrityFindr, which allows users to search for photos of celebrities on Twitter using facial recognition technology.

According to the announcement, Face.com will continue to support third-party developers.

"Now, lots of developers useA Face.comA technology to power various apps and make wonderful products...[T]he plan is to continue to support our developer community," the blog post reads.

Although the announcement did not reveal any specifics about what Facebook will do with the app company, the blog post hints that Facebook may look to tailor Face.com's technology to craft a mobile experience.

"We love building products, and like our friends at Facebook, we think that mobile is a critical part of people's lives as they both create and consumeA content, and share content with their social graph. By working with Facebook directly, and joining their team, we'll have more opportunities to build amazing products that will be employed by consumers," the blog post says.

Facebook revealed shortly before its lackluster IPO that it was not yet monetizing mobile users as effectively as it does desktop users.

Mobile is important in this context, according to Brian Blau, an analyst at Gartner, "because the key to getting faces online" is tapping the many cameras on mobile phones.

Facebook is probably also interested in acquiring Face.com's facial database, Blau said.

Privacy advocates see such growing databases of individual faces as a significant emerging threat to privacy. Sarah Downey, a privacy analyst with pro-privacy software vendor Abine, indicated that the technology was particularly alarming in the hands of Facebook.

"There is nothing more concerning in the privacy sphere than the marriage of Facebook and facial recognition," she said in an email. "Every time you're tagged, Facebook learns more about your face and how it looks with or without glasses, in various lighting, with facial hair, etc. It's one of the few data sources that Facebook has yet to monetize, and the acquisition of Face.com suggests that making money off your face is on their to-do list."

Cameron Scott covers search, web services and privacy for The IDG News Service. Follow Cameron on Twitter at CScott_IDG.