Such information, collected anonymously, is often used to provide services to the user and to allow for targeted advertising, but researchers say human movement patterns are so distinctive and predictable it is possible to identify a single user from just four instances of interacting with the network.
Humans' daily patterns of movement, seemingly random and unpredictable, can act as a kind of fingerprint of who is doing the moving, the researchers said.
Researchers at the Massachusetts Institute of Technology, working with colleagues in Belgium, analyzed 15 months' worth of anonymized mobile phone records for 1.5 million individuals.
Studying "mobility traces," the paths of each mobile phone, they found only four locations and times were sufficient to identify a particular user.
"In the 1930s, it was shown that you need 12 points to uniquely identify and characterize a fingerprint," study's lead author, Yves-Alexandre de Montjoye of MIT, told the BBC.
"What we did here is the exact same thing but with mobility traces. The way we move and the behavior is so unique that four points are enough to identify 95 percent of people."
The researchers acknowledged their findings will create concern about the benefits of technology versus personal privacy.
"We've really tried hard to not frame this as a 'Big Brother' situation, as 'we know everything about you.' But we show that even if there's no name or email address it can still be personal data, so we need it to be treated accordingly," de Montjoye said.