You might consider reading the section defining metadata as applied to telephone calls, particularly in the context of now knowing that the National Security Agency and/ or other government entities capture such information for each and every call, international and domestic. Former Vice President Dick Cheney and others take comfort in the fact that telephone metadata does not include a recording of the call.  However, this fact provides little comfort if a larger number of citizens—and voters—understand what is captured and cataloged.

            In current circuit-switched telephony, carriers set up a temporary, dedicated pathway between call originator and recipient.  Metadata data identifies the telephone company switching facilities used to create a complete link. Put another way, because the location of telephone switching facilities are known—and do not move—telephony metadata provides an accurate report on the location of callers and call recipients.

            The Second Circuit did not address the Constitutional (First Amendment and Fourth Amendment) implications of such data gathering. Had the court done so, it quite likely would have held that government has no lawful authority to track who associates with whom, absent probable cause that one or both telephone users have, or soon will commit a crime.

            A metadata capture program for every call captures information that violates the privacy expectation of citizens as well as their right to associate with anyone free of government cataloging. 

            Would citizens tolerate a government program that compiles the name and address of each letter writer and letter recipient?  Such information may be necessary for the Postal Service to route and delivery letters.  Additionally this information is quasi-public in the sense that it lies on the envelope and not inside it.  But who would support a massive investment of time and money for a government program to record such metadata?