The Main Street Garden park works because it enables this sort of contribution to the public realm by a large variety of actors, according to Patrick Kennedy.
"Who added the ping pong table? It is irrelevant. Who cares. What matters is that the park is shape-shifting. Adapting due to the individual actions of its numerous agents, including just the regular users. That is emergence. Cities are the amalgam of millions of numerous actions often acting independently. Somebody said, "I would like a ping pong table here." And there it appears.
It may come. It may go. But you know a place has come alive when it becomes the result of numerous actors, a superorganism comprised of the actions of individual organisms. It starts to have a life of its own. Constantly adapting to and adapted by its surroundings."