George Dyson writes in his article, "NSA: The Decision Problem":
The ultimate goal of signals intelligence and analysis is to learn not only what is being said, and what is being done, but what is being thought. With the proliferation of search engines that directly track the links between individual human minds and the words, images, and ideas that both characterize and increasingly constitute their thoughts, this goal appears within reach at last. "But, how can the machine know what I think?" you ask. It does not need to know what you think—no more than one person ever really knows what another person thinks. A reasonable guess at what you are thinking is good enough.
Data mining, on the scale now practiced by Google and the NSA, is the realization of what Alan Turing was getting at, in 1939, when he wondered "how far it is possible to eliminate intuition, and leave only ingenuity," in postulating what he termed an "Oracle Machine." He had already convinced himself of the possibility of what we now call artificial intelligence (in his more precise terms, mechanical intelligence) and was curious as to whether intuition could be similarly reduced to a mechanical procedure—although it might (indeed should) involve non-deterministic steps. He assumed, for sake of argument, that "we do not mind how much ingenuity is required, and therefore assume it to be available in unlimited supply."
And, as if to discount disclaimers by the NSA that they are only capturing metadata, Turing, whose World War II work on the Enigma would make him one of the patron saints of the NSA, was already explicit that it is the metadata that count. If Google has taught us anything, it is that if you simply capture enough links, over time, you can establish meaning, follow ideas, and reconstruct someone's thoughts. It is only a short step from suggesting what a target may be thinking now, to suggesting what that target may be thinking next.(Emphasis in original).