Ok let's try this: What if wearable cameras the police are using do this? What if I mounted a phone around my neck with the camera facing out, and used it to record everything it saw, and then compiled my own database of facial features, comparing, recording, etc. [0] The problem is that in public you have no expectation of privacy. Same with private communities (and some private citizens)[1] using license plate readers. I think eventually we're going to reach a point where facial recognition, and public recording will be omnipresent, in private hands, and we either ban cameras in public, or...stop going outside.

[0]. https://www.ted.com/talks/pranav_mistry_the_thrilling_potent...

[1]. https://arstechnica.com/information-technology/2015/12/new-o...