[doomlaser]

Beat me to it. Though I find the tone of this article incredibly overparanoid.

I'll also link along http://roguemaobea.com. They produce a line of audio apps that can hijack and route sound in OS X for a range of actually useful purposes. They've got tools for doing timed recordings of system audio, Line in audio, or audio from specific apps, as well as a tool for broadcasting any of these audio sources to Apple's Airport Express.