But phone calls are not supposed to be public

You'd think that, but you'd be wrong. Since Smith v. Maryland (1979) the standard has been that you don't have an expectation of privacy in the records of the calls you make (as opposed to the content of those calls), on the grounds that you necessarily share that information with the phone company. This is analogous to not having any expectation of privacy on the street, eg which friends you choose to visit or which places you go that could be observed by third parties, or the lack of privacy in who mail letters to, which information is shared with the post office.

(http://en.wikipedia.org/wiki/Smith_v._Maryland)

Now in 2006 Congress decided that consumers should have such privacy after all, and amended the telecommunications act of 1934 to make it illegal for phone companies to sell or share subscribers' call data, but that law contains a broad exception for law enforcement and intelligence gathering activity.

http://www.gpo.gov/fdsys/pkg/BILLS-109hr4709enr/pdf/BILLS-10...

Here's a good (non-jargon) summary of the arguments on both sides from late last year: http://www.courthousenews.com/2012/10/03/50935.htm From the legal standpoint, it's important to bear this context in mind, rather than assuming the current situation is the result of massive overreach by this administration, or the government since 9-11. The fact is that the NSA of today sits atop foundations dating from from the Cold War

By chance I picked up a 70s spy novel at a thrift store the other day, and it's all about Soviet sleeper agents hidden in the US and activated by coded messages in telephone calls - the heroes are in a race against time to pinpoint the origin of the calls and interrupt the planned sequence of events. I happened to notice the book because I remembered being scared of the movie trailer as a kid since it seemed to suggest that calling the wrong number could result in a violent death (https://www.youtube.com/watch?v=-Qg0w8qbBQo). So in the book the author was clearly worried about the openness of US society providing America's enemies with the tools of its own destruction - not unlike today's anxieties over cyber-warfare - and there's an implicit argument that high speed communications infrastructure is too powerful a force multiplier not to be under government supervision. Agree or not, it presented a surprisingly prescient understanding of asymmetrical warfare, to the point of seeming like domestic propaganda.

I mention this not to justify current NRA data collection, but to offer some historical context for how the law came to be the way it is. Too often, privacy discussions on HN are pendant on mythical notions of privacy being considered sacred until very recently. Historically (and going back all the way to the country's founding) the scope of the 4th amendment has been a lot narrower than people imagine and courts have generally not given much weight to the idea of a right to privacy. The notion that the Constitution provides a right to privacy wasn't articulated by the Supreme Court until 1965, in Griswold v. Connecticut (a case about birth control that paved the way for Roe v. Wade). See http://faculty.ncwc.edu/mstevens/410/410lect16.htm for a good overview. Griswold is still considered bad law by a lot of legal scholars, who think that any right to privacy needs to be added to the Constitution by amendment rather than extrapolated by judicial imagination.