What is a reasonable expectation of privacy?

The Obama administration continues to insist that the NSA wiretapping programming, whose existence was recently revealed by Edward Snowden, is not only necessary to national security but also perfectly legal.  In particular:

[T]he alleged metadata program is fully consistent with the Fourth Amendment. Most fundamentally, the program does not involve "searches" of plaintiffs' persons or effects, because the collection of telephony metadata from the business records of a third-party telephone service provider, without collecting the contents of plaintiffs' communications, implicates no "legitimate expectation of privacy" that is protected by the Constitution.

I don't know about you, but if I call, say, a suicide prevention hotline from my home phone, I would certainly expect that to remain private, and I think that expectation is reasonable.

But leaving common sense aside here (as seems to happen all too often nowadays), the administration is wrong here on technical grounds.  The phone company is not a third party with respect to call metadata.  A phone call involves two separate acts of communication: the call setup, and the conversation itself.  These acts are, of course, related, but they are still two separate acts.  When I initiate a phone call, the metadata is generated as a result of a private communication between myself and the phone company.  There is no third party.

To see that this is so one just has to think back to the days when calls were connected by human operators.  In those days, both the call setup and the call itself involved talking to another human.  If the contents of my conversation with the target of my call is protected by the Constitution then surely the contents of my conversation with the operator is as well.  The fact that nowadays the operator is a machine does not change the protocol, nor the resulting expectation of privacy.

This is why we need fewer lawyers and more engineers running the country.