Critical Social Mass

What is necessary for a Wiki or other similar social venue to become and survive.

• might also be "called an OrganizedCoincidence?, with no leader, no organizers, and no membership"

Some have called wiki a SocialExperiment?, while others wonder how it can even exist, given the lack of rigid structure and the variations allowed to what few rules that exist to govern its existence.

WardCunningham has used this expression to define one of the things it takes to sustain a wiki.