Commentary by Bruce Schneier
In the United States, the concept of “expectation of privacy” matters because it’s the constitutional test, based on the Fourth Amendment, that governs when and how the government can invade your privacy.
Based on the 1967 Katz v. United States Supreme Court decision, this test actually has two parts. First, the government’s action can’t contravene an individual’s subjective expectation of privacy; and second, that expectation of privacy must be one that society in general recognizes as reasonable. That second part isn’t based on anything like polling data; it is more of a normative idea of what level of privacy people should be allowed to expect, given the competing importance of personal privacy on one hand and the government’s interest in public safety on the other.
The problem is, in today’s information society, that definition test will rapidly leave us with no privacy at all.