"Supporters of the National Security Agency inevitably defend its sweeping collection of phone and Internet records on the ground that it is only collecting so-called “metadata”—who you call, when you call, how long you talk. Since this does not include the actual content of the communications, the threat to privacy is said to be negligible. That argument is profoundly misleading.
'If you have enough metadata, you don’t really need content.’ When I quoted Baker at a recent debate at Johns Hopkins University, my opponent, General Michael Hayden, former director of the NSA and the CIA, called Baker’s comment ‘absolutely correct,’ and raised him one, asserting, ‘We kill people based on metadata.’"
(Via.) The New York Review of Books