Julian Assange , founder of the WikiLeaks, says...

that Facebook, Google, Yahoo are vehicles for global surveillance, affiliated with U.S. intelligence . Specifically this refers to Facebook which is the most terrible instrument has been invented for tracking people. In fact it is the most comprehensive database about people and their relatives and friends’ names, addresses, places they visited provided with its dates, interests, hobbies and much more. And all this stuff is available for the intelligence community in all countries. So, dear reader, take care, even if you don’t have reasons to worry. What is interesting,  we provide interested parties with our private information ourselves.