From the Guardian:
Police in Leeds are hoping to prevent an outbreak of internet-enabled mayhem after thousands were invited to a public pillow fight through Facebook.
Worried residents of the Hyde Park area contacted the city council and West Yorkshire police when they learned of the proposed pillow bashing, which is scheduled to take place on May 25.
Police have contacted the apparent organiser in the hope of preventing the “flash” event from getting out of hand. Earlier this month, an award-winning park in the city was damaged when 350 people gathered for a water fight, which was also organised through social networking websites.
A police spokesman said yesterday: “We have contacted the alleged organiser regarding this event and advised him to cancel it. We will be monitoring the situation to ensure that it does not take place. Any such events, especially those potentially involving large numbers of people, must be given the proper licence by the council in advance.”