I don't believe the NSA created bitcoin because they do not care about currency. The CIA might have a need to create it, the way TOR was created by US Navy Research Lab. But then Treasury would be against and so would the federal bank. The thing is, as much as people (not us on bitcointalk) want to believe, government usually do not know what his left foot is doing that would make his right foot go the opposite way. Many Black box projects are so secret that referencing it or even think about them would send you in jail. Look at the reaction from Lavabit. Can't talk about it. So financing a bitcoin black box project would not cost that much compared to a Los Alamos project or keeping all those people fed at Area 51 for all those years.

This could simply be the "virus escaping the lab" type scenario.