"If this kind of location data makes it easy to keep tabs on employees, it makes it just as simple to stalk celebrities. Their private conduct — even in the dead of night, in residences and far from paparazzi — could come under even closer scrutiny.
Reporters hoping to evade other forms of surveillance by meeting in person with a source might want to rethink that practice. Every major newsroom covered by the data contained dozens of pings; we easily traced one Washington Post journalist through Arlington, Va.
In other cases, there were detours to hotels and late-night visits to the homes of prominent people. One person, plucked from the data in Los Angeles nearly at random, was found traveling to and from roadside motels multiple times, for visits of only a few hours each time.
...
Location data is also collected and shared alongside a mobile advertising ID, a supposedly anonymous identifier about 30 digits long that allows advertisers and other businesses to tie activity together across apps. The ID is also used to combine location trails with other information like your name, home address, email, phone number or even an identifier tied to your Wi-Fi network.
The data can change hands in almost real time, so fast that your location could be transferred from your smartphone to the app’s servers and exported to third parties in milliseconds. This is how, for example, you might see an ad for a new car some time after walking through a dealership."
https://www.nytimes.com/interactive/2019/12/19/opinion/location-tracking-cell-phone.html
Reporters hoping to evade other forms of surveillance by meeting in person with a source might want to rethink that practice. Every major newsroom covered by the data contained dozens of pings; we easily traced one Washington Post journalist through Arlington, Va.
In other cases, there were detours to hotels and late-night visits to the homes of prominent people. One person, plucked from the data in Los Angeles nearly at random, was found traveling to and from roadside motels multiple times, for visits of only a few hours each time.
...
Location data is also collected and shared alongside a mobile advertising ID, a supposedly anonymous identifier about 30 digits long that allows advertisers and other businesses to tie activity together across apps. The ID is also used to combine location trails with other information like your name, home address, email, phone number or even an identifier tied to your Wi-Fi network.
The data can change hands in almost real time, so fast that your location could be transferred from your smartphone to the app’s servers and exported to third parties in milliseconds. This is how, for example, you might see an ad for a new car some time after walking through a dealership."
https://www.nytimes.com/interactive/2019/12/19/opinion/location-tracking-cell-phone.html