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.