​We couldn’t do without our mobile phones. This tiny computer goes everywhere with us, as our alarm, GPS and camera. How else would we transfer money, log workouts, store plane tickets or dictate a reminder for later? While we enjoy these conveniences, we may not fully know all that is going on in the background.

​Many of the apps we add to our phone not only rely on our location to give us the information we’re looking for but also make a note of and keep a history of it. The location history created through our phone every day reveals much about our personal habits. We can adjust the settings on our phone to limit how each app accesses our location information, and location services can be turned off for many apps. But, of course, some apps – like Find My Phone or Find My Friends – always need location services on.

​And to make things more complex, we don’t own our location information; it’s generated and owned by our cellular provider. This fact muddies the water in trying to keep track of our personal information. Many of these apps take our unique package of data and share portions of it in an anonymous format with third parties. A recent study shows that over 70 percent of apps relay data to at least one third-party service.

​Sometimes, this process is transparent and consensual, but other times, it’s not – and when it’s not, things can quickly get ugly. When news broke that Cambridge Analytica, a political firm that worked with the Trump campaign, had used Facebook data to glean location information, personal information and even personality traits from users, the social media titan was asked to testify before Congress on its privacy practices. Facebook has gathered over the course of its existence a vast array of information, ranging from the personal information you provide in your profile to your preferences as reflected in your activity on the platform to the operating systems and devices you’re using to access your profile. Responding to outrage at their cavalier attitude toward sharing user data, Facebook has solicited comments from users on revisions to their terms of service and data policy documents, which are intended to make the policies more accessible. These new versions do tighten up the access third parties have to data, but more than anything they reveal the extent to which your behavior is monitored and collected.

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​What else happens to our location data, and what are third parties doing with it? Marketers want to find their customers. Advertisers are interested in where you go and what you do so they can geotarget you with tailored advertising when you are near their stores. They also want to know your interests and general shopping habits so they can make their products and branding more appealing to you. Data brokers like Acxiom and others work to combine data for a more complete picture of the consumer, drawing from social media, company websites and offline sources. “I’ve talked to a lot of ad tech and marketing people, [and] for them location data is the promised stuff of the future,” says Gilad Lotan, now vice president of Buzzfeed’s data science team.

​We need to be aware of the potential in this extended use of location data. First of all, it has been demonstrated that an individual can be easily identified from “anonymized” location data. The data trails that we all create, when combined with publicly available data, can be almost as unique to us as our own signature. For example, if you own a home, your name and address are in public records, and when combined with simple location data, the package of information can quickly be tied to you.

​It should be comforting that most of us are not special targets of surveillance, but our greater concern is to protect against identity fraud. Burglars and bad actors shouldn’t be able to trace our location, and personal privacy is an important part of our freedom. And while it’s still unclear what repercussions will come from the Facebook reveal, one thing is for sure: how companies handle customer information and how customers think about it will never be the same.