Are you guys seriously getting your heads around a decentralised forum? Forums are things of the past and those that survive are because they were launched and were successful in the past. I think the only thing that hasn't completely killed them is that a lot of people forum during quiet times at work.
I don't see the feasibility of a decentralized forum as I cannot really picture how moderation of such will be possible and without moderation, it becomes easy for it to derail from the core reason it was created. One seemingly decentralized forum I know is 4chan but the reputation of such forum is not worthy of any serious business marketing purposes and navigating through the forum is extremely difficult and tiring.