I just found this. It seems that the OP basically wants a way to make phpBB into a limited social networking site. While I don't care one way or the other about that, it seems like it's been asked for in the past -- usually by gaming sites wanting to give each clan their own forum that they can make their own.
While it would require "forum admin" permissions, there would obviously be several others that they could use. For example, you would want to be able to handle group-related actions for your forums like adding and removing people to your forum's group as they were added to or removed from the clan or making people moderators for those forums (not Global Moderators, obviously).
Of course, if anybody is serious about this, they'll need to write an RFC. (I didn't see one linked to from here....)
P.S. So why hasn't the topic title been changed yet? I changed the subject of the post, but I can't do any more.