Generosity of the few

For a long time I felt that the only solution to the tragedy of the commons is structure - based on money or authority. I have a new contender now. This one is called generosity of the few.  It doesn't really works always but in many situations, generosity of the few is good enough to keep the system in balance. Few examples:

• After being stuck in a traffic jam for some time and before the police shows up, someone who is probably not even driving any vehicle, stands up and starts managing the traffic, all the while listening to the shouts of angry drivers.
• On roads without any traffic lights, someone just stops the car to let some pedestrians cross the road.
• Some people actually answer questions on StackOverflow.