I’ve been playing a little with iPhoto 09 Faces feature. It took almost 3 hours for my home dual processor G5 to go trough 15000 pictures and find all faces, but then it only took it a few minutes to learn how I look like and find me in several hundred pictures.
I don’t know how algorithms used in iPhoto compare to the ones used by security systems to track people in surveillance feeds. If they are somehow similar, we are kinda safe: while iPhoto did find a lot of matches, it’s probably less than 10% of the actual number of pictures with my face in them. It will probably improve in time by leveraging a larger number of models, but it still require quite a few human work.
What the software is very good at doing is recognizing that some groups of pixels are actually human faces. I lile the way iPhoto comes up with facewalls of faces, all cropped at the same size.
Hard not to wonder when Google will start running this type of code on their picture search site. With just a little “mechanical turk” contribution the precision will be stunning, and we will have to kiss another piece of our privacy goodbye.