Your wireless carrier knows where you are as you read this on your phone — otherwise, it couldn’t connect your phone in the first place.
But your wireless carrier also has a memory. It knows where you took your phone in the last hour, the last week, the last month, the last year — and maybe even the last five years.
That gives it an enormous warehouse of data on your whereabouts that can help your wireless carrier fix coverage gaps while revealing much more. Depending on the density of cell sites around you at any one point, the location data triangulated from them can not only highlight your home and office, but also point to the bars you frequented, the houses at which you spent the night and the offices of therapists you visited.
Source : Why carriers keep your data longer
