From the Intercept article its not clear why this type of data was collected from an Icelandic carrier. The linked graph appears to show 100 IMSI's from Iceland, as opposed to 100,000 from Somalia* and tens of thousands from Afghanistan. It's possible that the Iceland data was acquired incidentally because it happened to come from the same sources that were sending data on more interesting countries. It's possible that there's something of value to be learned in Iceland. I don't know. The Intercept gives us very little context as to the actual products that the intelligence agencies produce. [Edit: Page 11 of this document indicates that the acquisition of keys from Iceland and Tajikistan was unexpected and that those countries were not targeted: https://firstlook.org/theintercept/document/2015/02/19/pcs-h...]

I don't dispute the fact that the US government has intelligence-gathering priorities that don't involve terrorism. I would argue that at least one reason terrorism is discussed is that there are diplomatic consequences to saying one spies on foreign governments. I also agree with the more cynical view, that terrorism is cited as a rationale because terrorism is scary and something opposed by everyone the US is trying to convince.

I believe very strongly that the world would be a lot safer if the US government knew certain things like the intentions of the Russian leadership and the capabilities of the Russian armed forces. Or the state of the Iranian nuclear program and that country's negotiating position. Or what exactly is happening on the ground in the midst of all the chaos in Libya or Syria or Yemen.

The answers to these questions will determine the fate of entire regions of the world.

*A subsequent document puts a later figure for Somalia at 300,000.