Mac OS X 10.7.2 Build 11C74 - Loss of audio when inserting or removing device from audio jack
Identical to issue #1731 (closed) (closed), but I'm up to date on libao:
Initiating pianobar while using the macbook's built in speakers, then plugging headphones into or unplugging from the headphone jack results in complete loss of sound from pianobar. The app needs to be restarted to restore sound.