David Thompson, co-author of Wild West 2.0 (Amazon) and general counsel of ReputationDefender, blogged on The Volokh Conspiracy:
… facial recognition is quickly becoming available on a wide scale. For just one example, an application called Face.com allows Facebook users to use photo recognition to find their friends in photos (even if they have not been tagged, or if they have removed their tag). Using the tool, it’s often possible to find hundreds of untagged photos of your friends (or yourself) posted by other people.
The Face.com developers just released an API (programming interface) to allow other websites to use the same technology. So far, Face.com has restricted use of the technology to known faces, but nothing technological prevents them from using their database of hundreds of millions of Facebook photos to identify millions of people in public photos.
The results of just one company unleashing photo recognition on the Internet could be huge. There are more than 3 billion photos on the site Flickr.com , and billions more in the unstructured Web, on sites like Facebook, and in automated surveillance systems (every time you walk past a security camera, imagine your name being logged).
Read more on The Volokh Conspiracy.