1) Tell everyone you know about Pillow Fight!
2) Tell EVERYONE YOU KNOW about Pillow Fight!!!
3) Nothing in your pillow but pillow.
4) Don't hit anyone without a pillow.
5) Don't hit anyone operating a camera.
Feathers will fly at this fun, flash-mob type event. Leave it to a place like San Francisco to host the most visible incarnation of the Pillow Fight's flash-mob-esque gathering, and subsequent public pillow fight. I would say that a safe thousand people were milling around Justin Herman Plaza at Embarcadero and Market Streets in Downtown San Francisco.
More info about the 2019 events: http://www.pillowfightday.com/
Photos from previous Pillow Fight!
Follow for updates: https://www.facebook.com/pillowfightsf