Comment by cameldrv

Reidentifyig anonymized location traces has been common for many years in the gray data market world. If you have multi-year traces, it’s not too hard. You just need some sparse location data for the target and then if the sparse data matches the trace at 4-5 times you can be pretty sure it’s the same person.

For example, if you ever use public wifi, and you hit a web page with real-time bid ads on it, your ip address and tracking cookie will be reported. The IP can be geolocated, and presto, you have one time/location datapoint. Credit card transaction data can also be bought, and a cc transaction often gives you a location and a time.