Like gs said, everyone should keep in mind that the clans decide when the matches are played. Flexible match times and roster sizes, with a mix of all of the maps, modes and loadouts. There's really no reason to pass on this.
Here's the Facebook page: Starhawk World Domination. Clan leaders should make an effort to join this group. Message Damon (the admin of the group and the tournament) and let him know your PSN and that you and your clan would like to participate.