Writing in the Washington Post, Posner argues that innocent parties’ privacy is not really generally being invaded by data-mining to find terrorist communications:

The collection, mainly through electronic means, of vast amounts of personal data is said to invade privacy. But machine collection and processing of data cannot, as such, invade privacy. Because of their volume, the data are first sifted by computers, which search for names, addresses, phone numbers, etc., that may have intelligence value. This initial sifting, far from invading privacy (a computer is not a sentient being), keeps most private data from being read by any intelligence officer.