Prof. Pentland described an experiment his team did with people's mobile phones. “Today,” Prof. Pentland said, “five billion people are running around, carrying with them these little sensor packages.” You own one; I own one. Some of us own more than one.
Just using the anonymous location data, you could also identify a group of people who don't know each other, but show an identical pattern of behavior, i.e. work and live in the same neighborhoods, eat in the same set of restaurants, shop in the same set of shops etc.
Yash Talreja, Principal, The Technology Gurus