From an article entitled The Agency That Could Be Big Brother by James Bamford in The New York Times, Christmas Day, 2005:
Jokingly referred to as "No Such Agency," the N.S.A. was created in absolute secrecy in 1952 by President Harry S. Truman. Today, it is the largest intelligence agency. It is also the most important, providing far more insight on foreign countries than the C.I.A. and other spy organizations.
But the agency is still struggling to adjust to the war on terror, in which its job is not to monitor states, but individuals or small cells hidden all over the world. To accomplish this, the N.S.A. has developed ever more sophisticated technology that mines vast amounts of data. But this technology may be of limited use abroad. And at home, it increases pressure on the agency to bypass civil liberties and skirt formal legal channels of criminal investigation. Originally created to spy on foreign adversaries, the N.S.A. was never supposed to be turned inward. Thirty years ago, Senator Frank Church, the Idaho Democrat who was then chairman of the select committee on intelligence, investigated the agency and came away stunned.
'That [surveillance] capability at any time could be turned around on the American people and no American would have any privacy left, such [is] the capability to monitor everything: telephone conversations, telegrams, it doesn't matter. There would be no place to hide. If this government ever became a tyranny, if a dictator ever took charge in this country, the technological capacity that the intelligence community has given the government could enable it to impose total tyranny, and there would be no way to fight back, because the most careful effort to combine together in resistance to the government, no matter how privately it was done, is within the reach of the government to know. Such is the capability of this technology ...
I don't want to see this country ever go across the bridge. I know the capacity that is there to make tyranny total in America, and we must see to it that this agency [NSA] and all agencies that possess this technology operate within the law and under proper supervision, so that we never cross over that abyss. That is the abyss from which there is no return.'
-- Senator Frank Church (D-Idaho), 1975, quoted in James Bamford's The Puzzle Palace
Senator Frank Church was a prophet, indeed.