While pillow fights themselves have existed for as long as feather pillows have, massive pillow fights have been organized for fun or in an effort to break Guinness World Records. The flash mob version of massive pillow fights is distinguished by the fact that nearly all of the promotion is Internet-based. (thanx to wikipedia for this explanation) This originated in England and has spread world wide. The rules of Pillow Fight Club:

Rules:
1) Tell everyone you know about PILLOW FIGHT!!!
2) Wait for the set time before fighting
3) Don’t hit anyone with out a pillow (unless they want it)
4) Don’t hit anyone with a camera
5) HAVE FUN!!! (it's not a competition)

http://tribes.tribe.net/pillowfight