This is the biggest scandal no one cares about. I am involved in politics and the upcoming election, and was just demoed a service that was beyond creepy. Basically they provide a library that is widely used by developers, and by the saleswoman's account their stack was in an app on 80% of phones in the world. Android or iOS.
During the pitch she spoke of micro targeting people, and suggested we could see who was at a certain large political rally in DC for both of the last two years. While immediately creepy in its on right, I asked how her company could take supposedly anonymized info from location sharing and match it with an actual person. She replied that they simply geofenced the phones while people were probably asleep which after awhile gave away their home address. They could then match that location with voter files and people's names.
The implications of this one example were staggering to me. Would you suspect a popular game or restaurant app could be used to completely profile you by a third party? We do around here, but most people don't. They don't get the connections. But I asked is she thought people would be unhappy knowing that apps were being secretly being used to share such personal information. To her credit she said yes they would. And she admitted the service would be illegal in Europe.
In the end I told her that as a privacy advocate I wanted to throw up in the back of my throat (actual quote), but as an advisor to campaigns I would have to tell them to use the tech. You don't bring a knife to a data fight, and it's clear it's a data fight now.