Analog Information at Risk of Privacy Violations?

In response to Jimmy Carter's remarks to NBC about how he uses 'good old snail mail' when he wants to keep his correspondences private, VICE reported on the abilities of the US Postal Service to collect and track meta-data for posted mail.  Dubbed the Mail Isolation Control and Tracking program (MICT), it was initially used in response to anthrax and ricin being sent in envelopes through the mail.  The program acquires names, addresses, return addresses, and postmark locations among other things to develop a network or map of one's contacts.  As we've seen through various digital examples, a lot can be gleaned from the somewhat harmless seeming meta-data. 

An interesting reminder of how information does not need to be digitized for it to be used in ways that may harm the data subject or violate one's privacy.