As far as I know, face-recognition tech is illegal in law-abiding countries. Although it's probably mostly a legal impediment, I can imagine if the authorities

As far as I know, face-recognition tech is illegal in law-abiding countries. Although it's probably mostly a legal impediment, I can imagine if the authorities spotted an event and need to track a suspect, they can put all the footage into a system and it will return a sequence of videos/angles in which the suspect was seen.