Facial recognition is really scary. This was recently demonstrated for Russia's Facebook, VKontakte, when a service appeared that let you look up people on that site by photo. So people started looking up the profiles of random subway passengers, outing sex workers to their families and friends, etc.
I really don't like having my picture taken anymore. You don't where it's going to end up. I also do wonder how much infrastructure would need to be added in a country that already has a lot of video surveillance (like the UK) to implement a "find this person" feature, where you could just feed it a photo and it would go looking at all camera feeds.
Sort of happening now, in a way they couldn't imagine.