That algorithm is likely to stay hypothetical for some time. Facial recognition has a long way to go before it's practical. Your scenario also would require a lot more cameras being added at great expense, and/or cooperation among the many public and private entities that operate cameras.
I'm not without my own concerns about surveillance, but let's not celebrate someone's antisocial behavior simply because he claims to be making a point. I think filming with a tripod, if it's not aimed at anyone in particular, would be far less offensive, but useless as a demonstration for that same reason.
"That algorithm is likely to stay hypothetical for some time."
I interviewed someone a few weeks ago whose prior job was maintaining such an algorithm for use in shopping malls. They had a database that you could issue queries like "Given that a person goes to store X, how long on average will it be until they return?" or "Are women who shop at Victoria's Secret likely to visit The Gap in the same month?" and so on. His job was applying that knowledge to affect what ads were displayed on the video screens that people walked past in the mall.
(Yes, the project was self-consciously inspired by "Minority Report". Apparently nobody found that creepy.)
FWIW, Las Vegas casinos use facial recognition to recognize card counters and other 'undesirables.' One of my Dad's clients (he's an engraver) was head of security for Caeser's Palace and his assertion was that the cameras were 85 - 90% effective at picking up someone as they walked in the door, and 100% effective at identifying them if they loitered in the casino for more than about 15 minutes. Granted its anecdotal, its backed up by the guys who well these systems to Casinos promising this capability but still.
I've never had a chance to talk to them about false positives or negatives so I can't really put their numbers in perspective but they seem to project facial recognition as a 'solved problem.'
Your anecdote (and goodside's) are indeed a bit scary. Of course, tracking faces within an enclosed space (casino, shopping mall) is not the same as tracking someone's movement throughout a whole city. But maybe it could be applied on the streets of certain “high-crime”, downtown areas and spread from there. I admit I'm troubled by the thought of the executive power available when such a scenario becomes normal. We need to match this technological innovation with some form of social innovation that keeps police accountable, but obviously “who watches the watchers?” is a difficult and unsolved problem.
To track someone through a crowd, you don't necessarily need continuous facial recognition. You can tag the identity to a person once using facial recognition or other means (credit card or ATM use if you have that data), and then revert to a more basic motion tracking system to follow them around.
I don't know much continuous object tracking across multiple cameras, but I highly doubt it's a difficult problem as long as the cameras have some overlap.
I had a professor show me just this kind of algorithm almost 10 years ago, I have since seen other demonstrations of it as well. To find and follow a face is not hard, heck I can unlock my cell phone with my face.
Also claiming this is Anti-Social is the whole point, individuals can be called Anti Social because its easier for people to fight (be anti) them and make them conform. Governments and large corporations, on the other hand, are harder to fight and thus Society justifies allowing their behavior until enough people group to together to force a change.
This video is a metaphorical call to arms in that sense.