Thanks Dan. This article gave me an idea for a future game.
Combine the oh-so-last-year flash mobs with tangible interfaces and you
get Mob-and-Seek. Everybody buys a little device that just alerts when
someone else with the same device is nearby. You all mob to an area
downtown. You don't know who else is playing. If X people are near each
other (critical mass), one person's device automatically buzzes "you're
it." Everybody else buzzes "you're not it." They then have to figure out
who else is playing (who looks paranoid?) and tag them It. Everybody
buzzes It or Not It and another round begins. When critical mass drops
off, everybody buzzes Game Over.