Total Immersion: Flash mobs don't take place in sterile stages, isolated from the audience. Performers are right there where the action is, unafraid to recruit new members and train them "on the spot."
Joy: Flash mobs are often joyful events, a beautiful culmination of hard work and preparation. Performers work for free, as a gift to the audience. Just look at the faces of the performers in the "Somebody to Love" video - they seem to be having an amazing time.
Collaboration: Flash mobs are no different than any other perfectly executed team project. The main job of each team member is to make other members "look good."
Planned improvisation: Something as beautiful as this "Somebody to Love" performance is the result of hard work. I can only imagine the number of rehearsals and planning sessions to get the performance just right! Flash mob participants, however, must be ready to improvise. After all, they will be performing in a public place, coping with the unpredictable reactions of the public. The whole experience reminds me of teaching advice I received from colleagues from University of Minnesota once - "Plan like crazy, then let it go!"
Courage: It takes courage to perform unannounced and unexpected. What if someone doesn't like the performance? What if someone is just busy and feels like the performance is an inconvenience? Flash mob performers ignore what ifs. They just do it.
What does all this have to do with community building? Well, first, one does not build a community from a sterile place. One must be willing to engage with community members, interacting with people in their natural settings. Joy is a critical ingredient - I can't imagine growing a community without a sense of energy, excitement, and pure fun. Collaboration and planned improvisation are vital for founders and early members, who must work together in the background to make things happen. Then, collaboration becomes critically important as the community grows. Finally, courage is an invaluable final ingredient. Everyone must be ready to take risks, tolerate some level of failure, and move forward when things don't work.
What are your own best practices for building a community?