Before I retired I worked on a project for Australia's equivalent of America's Homeland Security Department. You have ABSOLUTELY NO IDEA what's going on behind the scenes!
The things Australia was doing with telephone data made us shiver with the reality of it all. Their tracking system identified all phone communication people had with each other within the country - in REAL TIME (this required massive systems with massive amounts of physical memory and massive semiconductor I/O systems)!
Their tracking system also tracked ALL incoming and outgoing calls into Australia. Suppose you lived in a foreign country and called a hotel in Australia to book a reservation. Their system would log your number, and if the foreign nation agreed to cooperate and share its own phone data, Australia's tracking system would identify all the phone numbers that "touched" the number making the hotel reservation.
But it doesn't stop there. Say your son called Australia for the hotel reservation. You, being the parent, you are linked to his phone.
But it doesn't stop there. All numbers connected to the parent's phone get tracked as well. And all numbers for the parent's friends got tracked, to their contacts, then to their contacts, then to their contacts, and so on and so on.
Basically, the tracking system was a gigantic upside down pyramid that was theoretically capable of identifying relationships for EVERY PHONE NUMBER ON THE PLANET.
Be scared, be very scared.
Scott