what do Americans think about the NSA scandal

[Mavfin]

Technically, Windstream didn't even have to sell you out.

An unlisted number, just means that your number isn't published PUBLICLY. Meaning, that your number isn't sold to companies, it isn't available in the public domain. As the IRS is part of the US Government, they aren't part of the public domain. And since Caller ID has been a standard feature for most since the 1990's, it's not illogical to think that the USG has better Caller ID, that removes the blocking restrictions of an unpublished number.

Knowing what I know about telecommunications and network security and programming, your theory is likely right on the money. The caller-id system is programmed to give information, not withhold it. By default, it will give your number. It only hides it when actively told to do so, or actively blocked by other parameters in the system. Do you imagine there's any blocking of caller-ID on IRS phones? Generally, blocking caller-ID at the entrance to a corporate VOIP system isn't necessarily by default. I've heard from my network cohorts of them having to call <big phone co> so that caller-id blocking actually worked on the internal VOIP phone system for customers who wanted it to.

That's not even sinister. It's just programmers wanting their code to work, and not thinking about how some customers wouldn't want it to work.