More for that warm feeling of total security, as reported in the New York Times, about:

the Mail Isolation Control and Tracking program, in which Postal Service computers photograph the exterior of every piece of paper mail that is processed in the United States — about 160 billion pieces last year. It is not known how long the government saves the images....

The Mail Isolation Control and Tracking program was created after the anthrax attacks in late 2001 that killed five people, including two postal workers. Highly secret, it seeped into public view last month when the F.B.I. cited it in its investigation of ricin-laced letters sent to President Obama and Mayor Michael R. Bloomberg. It enables the Postal Service to retroactively track mail correspondence at the request of law enforcement. No one disputes that it is sweeping.

“In the past, mail covers were used when you had a reason to suspect someone of a crime,” said Mark D. Rasch, the former director of the Justice Department’s computer crime unit, who worked on several fraud cases using mail covers. “Now it seems to be ‘Let’s record everyone’s mail so in the future we might go back and see who you were communicating with.’ Essentially you’ve added mail covers on millions of Americans.”

Law enforcement crows about how important the program has been to find a ricin-mailer, a prostitution ring, and drug smugglers (the latter two the kinds of crime for which surveillance is so often needed, as it often lacks victims).

Don't worry, they need a warrant to open the mail. (Unless they don't):

Law enforcement officials need warrants to open the mail, although President George W. Bush asserted in a signing statement in 2007 that the federal government had the authority to open mail without warrants in emergencies or foreign intelligence cases.