Exactly, this is what the NSA wiretapping case was about. They weren't listening in on all the calls, they were gathering information on who was calling who an

Exactly, this is what the NSA wiretapping case was about. They weren't listening in on all the calls, they were gathering information on who was calling who and for how long. This is the most traditional wiretap because it requires a lot less effort and provides a lot of information.