That's what your social network is for in your profile. :)
What I had in mind was something based on "social network" concept.
(food for thoughts)
- x number of posts and/or rep points allow member to form a club
- each club has custom name
- each club has custom avatar (or banner, logo, badge, flag...)
- each club has it's own exclusive forum with threads (crossbreed of private messaging and posting)
- post/thread lifespan in those forums are time-limited (a week, for example)
- each club member gets (optional) mini-badge along his/her avatar
- founders have administrator powers within the clubs (kicking ppl out, deleting posts or threads)
- clubs survive only if they have x number of club members.
On the second thought, it would be pretty pointless.
Another unrelated suggestion:
Beside PMs (in the header), useful thing would be number of new subscribed threads.