A lot of geolocation data on the market is anonymized, following medium-lived unique IDs that aren't able to be mapped to other identifiers. The problem with that is that if you have precise locations, or enough samples that you can apply statistics to find precise locations, in many cases you can de-anonymize the IDs. You can purchase address and resident listings from a number of different data vendors, and by chec…
I think a lot of people don't realize the power of a big enough sample size. With enough samples even something pretty innocent looking like your daily step counter could make you identifiable.
As far as I know we don't have large enough databases to make this happen in practice, but I don't think this is impossible in the future.