On the other hand, I've noticed a couple of companies using their own Stack Overflow install for their support forums, and I'm sure that could work pretty well. It's not a question of the software, just whether or not the community is right, really. SO's has ended up with too many volunteer bureaucrats, I think, and to make things worse there's even a meta site where they can gather and make up more rules for people to follow. You say organised, I say ossified... well, let's call the whole thing off. I stopped posting on SO after my last experience.
I don't expect anybody to care about one person leaving (and nor should they!) but if enough individual people leave, then I guess eventually nobody will be left.