C|NET has a FAQ on NSA DataMining

excerpt:

Q: What about Internet communications, such as Internet telephony or e-mail messages?
Much of the Internet traffic that's transmitted in the United States traverses just a handful of switching centers owned by big communications companies, such as Verizon. The busiest are MAE East (Metropolitan Area Exchange), in Vienna, Va., and MAE West, in San Jose, Calif. The NSA has access to those switching centers, Bamford says.

In addition, the Federal Communications Commission has ordered broadband providers to build in back doors for electronic eavesdropping.