Check out the following articles for more information:
- The Agency That Could Be Big Brother (New York Times)
- Spy Agency Mined Vast Data Trove, Officials Report (New York Times)
- Big Brother is watching (The Oakland Tribune)
- Fear destroys what bin Laden could not (Miami Herald)
According to the articles, the communications being monitored are those that are international. They eavesdrop on suspected terrorists but mine the data on many more international calls.
As someone who makes international phone calls to a close friend, I don't like the idea that my phone calls may be monitored by the U.S. They are already being monitored by my friend's country of residence, and it is no fun having to watch what you say. It is surprising how much some of the taboo stuff can come up in completely innocent conversation.