Quick question: When was the last time you had a pillow fight? If the answer to that question is over 365 days, you obviously have been missing out on one of the most prominent "only in San Francisco" events that happens every Valentine's Day--the Flash Mob Pillow Fight in Justin Herman Plaza.

When the clock on the Ferry Building strikes 6:00, mayhem ensues as thousands of people crowd the Plaza and have a massive pillow fight. The event, which celebrates its third incarnation this year, has garnered massive media attention around the world and is attended by spectators and participants alike. This is one of the most unique ways to spend your Valentine's Day, so grab a pillow and head to the Justin Herman Plaza to partake in one of the most whimsical events San Francisco has to offer.

For more information, check out the Pillow Fight website.

Last year, Metrowize covered the event. Check out what we caught and what to expect this year.