However for posterity it's clear that the NSA is not about terrorism:
* The Inspector General Report on the Boston Bombings and the US's failure to discover them do not talk about the NSA (except to mention it in passing just two times). "We focused our review on the entities that were the most likely to have had information about Tamerlan Tsarnaev prior to the bombings – the FBI, the CIA, DHS, and NCTC, which maintains the U.S. government’s database of classified identifying and substantive derogatory information on known or suspected terrorists."
* The NSA's mission statement itself is "The National Security Agency/Central Security Service (NSA/CSS) leads the U.S. Government in cryptology that encompasses both Signals Intelligence (SIGINT) and Information Assurance (IA) products and services, and enables Computer Network Operations (CNO) in order to gain a decision advantage for the Nation and our allies under all circumstances."
* The NSA's actions regarding the Natanz nuclear processing facility, capturing data from German officials during the Eurozone crisis, of off shore oil drilling bids from Brazilian PETROBOL, programs such as HACIENTA that specifically target countries, blatant references to political and financial targets, etc
* Programs such as QUEEN, ORCHESTRA, MINERVA, BIRDSONG/BADGER/GATEWAY/SLIPSTREAM, JTRIG, literature and research on social contagions and PsyOps (related to recent recent USAID Cuban Twitter project and Lincoln Group)
Together these tell us that the NSA is an arm of us finance, espionage, sabotage and influence/propoganda targeting political upheaval in target nations.
http://kieranhealy.org/blog/archives/2013/06/09/using-metada...
If you want to know what the FBI does with guns, you can't just inspect what their guns are capable of. You have to look at their mission statement, their actions, their other technological investments, reviews and investigations of the FBI, etc.
The NSA works with bureaus that handle domestic terrorism. They provide some small tools and data for that. Some selectors and social analysis of phone metadata are surely part of that. But if you look at what the NSA does, what their capabilities are, what their mission is and objectives are, and reports about their internal posture and attitudes you quickly learn that their programs are not broadly about counter-terrorism, although sometimes they partner for these purposes.