I heard a talk once from some guy working for a company who analyzes this data (it had something to do with transportation of people; where it would be most eff

I heard a talk once from some guy working for a company who analyzes this data (it had something to do with transportation of people; where it would be most efficient to have a new bus route and such), some of the regulations are actually rather interesting (Europe). E.g., location-specific data is not allowed to be sold if the amount of data points is below a given threshold, to avoid de-anonymization scenarios such as the one you have mentioned. Granted, I have no idea how well the regulations actually work, but it did sound as if quite a bit of thought went into it. Thinking about this, I wonder if companies providing smartphone apps with invasive tracking are upheld to the same standards...