It is only a short step away from using the system to compare faces to mugshots to using it to compare faces to DMV photos. I believe the system is already designed to attempt match every person that walks by to their DB of mugshots so the processing power is there. Sure, the more photos you have to compare to the more power you need, but I don't think it would be impossible. The bigger obstacle would probably be storage space - I would imagine keeping track of every match of every person would take up what would be an unthinkable amount of storage today, but does anyone else remember paying several dollars per megabyte for say, a 100MB HD not all that long ago?
First it'll just be used to catch the big nasty criminals - they'll probably even make sure the first arrests are murders, rapists, etc. so we all get used to the technology and realize how "good" it is. Next, they'll probably say it will help us find lost children or somesuch (hmmmm.... "for the children" - where have we heard that before?). Next, we'll all be standing in line to take photos for our bank - there will be FaceIt or some other competing technology in every single store - ostensibly to verify your identity when using your CC, but I would imagine this will be an invaluable marketing tool for companies as well.
Once they prove how helpful the technology is by catching all the murderers, saving all the children, and ridding the world of credit card fraud, it will be used for more nefarious purposes. I don't doubt that sometime in the (near?) future there will be a camera on every corner, and every time we pass, a new record will be added to our file. With the hundreds of millions of people in this country, chances are no one will ever look at your record, but I'd rather not take that chance. How hard would it be to set up one of these systems in front of your favorite gunshop?
Rocko