My company perfomed audio ballerinas in the early 90s with Benoit at the Cleveland Perfomance Art Fest.
It was a blast. We dragged the lawn rakes with pick up mics on them though the new fancy mall downtown which made a deafening screechy noise as the dancers in black unitards, high heels and dark glasses paraded like mute Barbies. Later that evening, we changed the frequency on the tutu's recorded loop by adjusting the rheostat on the bar lights the dancers stood under. The the more light the solar cells recieved, the faster the loop played! It was awesome! One day in a busy downtown food court, we played 6 different radio stations at once as we meandered through the crowd.
We did about four different perfomances over the course of the weekend.
Those were the days!

A member of FlashmobUF showed me this article today. I wish I had found it sooner! I think I can answer some of your questions. Since starting Flashmob UF in the Fall of 2004, the group sees a huge spike in membership after each Mob. I credit this to word of mouth. One current member tells a friend to be at the site of a Mob, said friend sees Mob, then the friend joins. I think, whether in a college setting or elsewhere, like a large city, it's the idea of escape from the usual routine that gets them involved. You mean I can spend 3 minutes going from boring class A to boring class B and participate in a giant conga line for no reason? Sign me up!

Your 6th graf nails it. People see the group and they want in. They see it almost as a secret society, with only a few people who know what's going down until it goes down. Leveraging digital communication tools? You bet! I use a Facebook.com group to organize each Mob. Only members receive the messages with instructions. Also, the main reason for this video's large play on youtube was it's video game nature. Once video game bogs and sites got a hold of it, the hits just kept on comin.

Combining a dance performance would easily work with a large dance troupe. As long as the performace comes from nothing and disappears as if nothing happened, you got yourselves a Mob. The audience, like our audiences, become intrigued. They want to know why this strange event has happened, and they will do their research to find out.

I know it has been a while since this post was made, but I hope this helps answer your questions. Feel free to e-mail me at PDuffy01@ufl.edu if you have any more questions.

Sal "The Man in the Orange Hat" Picataggio, Founder, Flashmob UF