After 9/11, Congress loosened restrictions on national security letters (NSLs), a kind of administrative subpoena, first authorized in 1986, that the FBI uses to demand information from phone companies, Internet service providers and financial institutions. According to the Justice Department's inspector general, NSL "requests" skyrocketed from a total of 8,500 between 1986 and 2000 to more than 56,000 in 2004 alone.

The Obama administration has made liberal use of NSLs, which in 2010 allowed the FBI to peruse information about 14,212 American citizens and permanent residents — a new record — without bothering to get clearance from a judge. If you were one of those people, the odds are that you will never know, because NSLs are almost always accompanied by instructions that prohibit recipients from discussing them.