Setting who wants to do this aside in order to avoid the constant 'X is worse than Y' arguments. I don't think it's unreasonable to assume that in a near future we will have cameras that can do much more than identification on a massive scale. It may be easy to track things like how stressed, healthy, sober etc. people are without their consent or without them even noticing. And this would be precise , not speculativ…
Yup. Think about how you can recognize your friends without even seeing their face, by the way they walk, what they wear, how tall they are, and other contextual clues. Computers will be able to do all of that. Also think about other things that only computers with massive amounts of data will be able to do. Computers will be able to enumerate your wardrobe, your possessions. They'll be able to figure out most of the…
Yep, but think also how many times you approached a friend from behind and patted him/her on the back only to realize that you just patted a perfect stranger?
I have no particular problem to believe that one's gait is "distinctive", but quite a few in believing that that particular stroll is "unique".