A play on the phrase tragedy of the commons
. In the tragedy of the commons, each person tries to maximize their own benefit, and the end result is that everyone loses because of overutilization of limited resources. In the comedy of the commons, each person, while getting something for themselves, also (directly or indirectly) contributes back to the common good at the same time.
BitTorrent makes use of the comedy of the commons, since the more people who participate, the better the service gets.