I think primarily it's like any other shooter where it's easier to play with friends and such. I remember hearing rumors of private quarters at the Tower for each clan. Essentially I think Bungie's laying out the foundation for meta-gameplay, where the player community builds up the extra activities and organizations, using the game as a framing device. This assertion may be validated by the fact there's going to clan-alliances and Crucible tournaments. If you look in your page (I think in the admin tools) there's a space for "clan-features" and will be enabled at launch. Bungie will probably release new information as the game progresses and make new developments as the player community expands on the all the possible ideas within game. That's all I got at the moment. Good luck with your clan and watch out my mind, the Exiled Blades. Hope this helps!