This is no different than a spotter LEO or witness recognizing you from a mugshot or from video surveillance. It's just that it's done with EVERYBODY now.
Consider the following example. Calling someone to ask them on a date is normal acceptable behavior. Doing it 20 times an hour, 3 hours a day, every day, quickly becomes immoral and illegal.
Not if you're calling different people, totally legal.
What is n for facial rekognition?