> Constitutionally, privacy is a pretty cut-and-dry concept.

That's true. Privacy is anything you kept on your own person or in your own property.

Emails however, are stored on another person's computer and therefore have no expectation of privacy. (some 1980s case IIRC).

Constitutionally, privacy is a cut-and-dry concept for the 1800s when the Bill of Rights were written. The fact of the matter is, the people who wrote the Constitution had no concept of "Cloud Computing" or "Computing" in general.

So it is up to the job of today's Politicians and Judges to figure out what to do in these cases. And that isn't a very easy job to do.