NYTimes on Location Tracking
The New York Times published a fantastic exposé and data visualistion site about the scale of gathering and selling of location data. They obtained a file with 50 billion location pings of 12 million Americans and sifted through the data in horror. The data can be bought from data aggregation companies that offer data collected from apps on your smartphone, like news or coupons apps, not from telecom companies or the big tech companies.