http://media.ccc.de/browse/congress/2014/31c3_-_6249_-_en_-_saal_1_-_201412271715_-_ss7_locate_track_manipulate_-_tobias_engel.html

Companies are now selling the ability to track your phone number whereever you go. With a precision of up to 50 meters, detailed movement profiles can be compiled by somebody from the other side of the world without you ever knowing about it. But that is just the tip of the iceberg.

Tobias Engel