(Thanks to NoCamels) Israeli Startup Groovideo’s application and web based service allows you and your friends to produce different clips for the same film simultaneously in easy steps. You upload all the clips and Groovideo combines all the segments into one final video.
http://nocamels.com/2012/07/startup-groovideo-edits-group-videos-into-simple-films/
http://www.youtube.com/watch?v=P4qlb0lD4kg&feature=player_embedded