On story, Splash Damage didn't want to just make it "hero cops versus evil terrorists" or "heroic freedom fighters versus the evil oppressive forces." Instead, the developers opted for two factions that both have good reasons to fight and are both justified in their actions.
Brink is scheduled for a Spring 2011 release on the PC, PS3, and Xbox 360. It will be shown off at QuakeCon 2010 later this week.
why the long face, brink?
I see what you did there.