Do you understand.
The Face.com platform uses our own proprietary technology to detect and recognize people's faces in photos. We have geared our technology towards high accuracy in everyday photos, and are able to scale it to billions of photos a month. The various Face.com services mash-up existing platforms such as Facebook in order to provide tagging, and as such requires your specific Login credentials in order to process photos within your friends social network. As a cloud technology, developers sign up for free and start incorporating the Face.com capabilities without installing any software, focusing only on building a great user-experience.
While we cannot reveal all our secrets behind our great technology, we regularly contribute work to academic research. If you're interested in learning more about the underlying algorithms head over to the Labeled Faces in the Wild, a great resource for most recent approaches to face recognition and where we publish our papers.