For those of us who have already forgotten or have never known the reason for its necessity, could you explain why? Internationally and historically, similar levels of state communications monitoring are correlated with the need for self-preservation by authoritarian regimes. There are also many modern day states which do not possess an agency directly analogous to the NSA.
Would you be happier if I said I expect cyber-sabotage, cyber-espionage, and cyber-subversion to be important parts of future conflicts?
I'd imagine there are others like me.
I think it is a legitimate question how much of an offensive information warfare standing capability a country needs when not at war, and what level of dirty tricks intelligence agencies should pull in peacetime to monitor adversaries. Particularly due to the non financial costs of this monitoring -- losing our moral standing as a free and fair country, incidentally monitoring citizens or those present in the USA, in violation of the constitution (especially due to the tortured "five eyes" sharing agreements, which, if they weren't governments, would be viewed as a conspiracy and some kind of constructive crime), etc. I judge all of this stuff by "does it make us safer", and at some point, it clearly goes the other way. I think that point is several hundred billion dollars a year less spending than what we have now (well in excess of a trillion). Maybe 50-75% less spending.
The NSA does some questionable stuff, but it also does some awesome stuff. The first thing that comes to mind is SELinux.
On a tangent, don't forget that we need an organization like the NSA (or at least like what the NSA should be). The more ubiquitous computing becomes, the more important that role will become. So, don't advocate chopping off a head of the Medusa; advocate fixing what you see as wrong.