This would be relatively difficult for Manhattan, some parts of the outer boroughs though are a different matter. I was concerned when this first hit HN becaus

This would be relatively difficult for Manhattan, some parts of the outer boroughs though are a different matter. I was concerned when this first hit HN because I have a friend that lives in a fairly sparsely part of town and his (now ex) girl friend has a possessive ex-husband that doesn't like her seeing other men. He isn't going to be able to make sense of the data himself, but if someone weaponizes it the way you are talking about it could be a real problem for people with stalkers/psycho-exes.