Face.com announced the release of their API this morning:
In this open alpha stage, we’re letting any developer tap into our face detection and face recognition tech through simple REST API calls. Whether you’re looking to build a cool photo tagging application, create personalized e-cards or campaigns, or any other sci-fi idea that comes to mind, we’re here to serve.
via Announcing our new, free, open API | face.com.
What it means: how about a mobile application which enables you to take a picture of someone you’re meeting face to face, recognize that individual and download that person’s contact information (with their permission) in your phone instantly. That sounds like the evolution of traditional people (white pages) search, no? Seems like there would be dozens of ideas to reinvent people search with such an API.
Seb Provencher's Blog 
And imagine a camera at the entrance of a store: it can recognize you and send to your phone personalized promotions based on your previous purchases…
Privacy thoughts put aside, this sounds like a good idea with a potential to re-energize people search. Besides that you might have a look at a Swedish service called Recognizr .