If you haven't seen this USA Today interview with three former NSA employees, then I strongly suggest you watch it:
Still skeptical? Read this blog post about a March of 2008 news story in the Wall Street Journal, which printed:
"Largely missing from the public discussion is the role of the highly secretive NSA in analyzing that data, collected through little-known arrangements that can blur the lines between domestic and foreign intelligence gathering... the spy agency now monitors huge volumes of records of domestic emails and Internet searches..."
And, I really want to call your attention to the following from the same news story:
"A number of NSA employees have expressed concerns that the agency may be overstepping its authority by veering into domestic surveillance. And the constitutional question of whether the government can examine such a large array of information without violating an individual's reasonable expectation of privacy..."