"This is really fundamental in the sense that now we're operating at high resolution, the trade-off is how useful the data are and if the data can be anonymised at all. A traffic forecasting service wouldn't work if you had the data within a day; you need that within an hour, within minutes."

Dr Hidalgo notes that additional information would still be needed to connect a mobility trace to an individual, but that users freely give away some of that information through geo-located tweets, location "check-ins" with applications such as Foursquare and so on.

But the authors say their purpose is to provide a mathematical link - a formula applicable to all mobility data - that quantifies the anonymity/utility trade-off, and hope that the work sparks debate about the relative merits of this "Big Data" and individual privacy.

Sam Smith of Privacy International said: "Our mobile phones report location and contextual data to multiple organisations with varying privacy policies."

"Any benefits we receive from such services are far outweighed by the threat that these trends pose to our privacy, and although we are told that we have a choice about how much information we give over, in reality individuals have no choice whatsoever," he told BBC News.

"Science and technology constantly make it harder to live in a world where privacy is protected by governments, respected by corporations and cherished by individuals - cultural norms lag behind progress."

But Mr de Montjoye stressed that there is far more to location data than just privacy concerns.

"We really don't think that we should stop collecting or using this data - there's way too much to gain for all of us - companies, scientists, and users," he said.

"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."