Reddit is a useful concept: a series of communities with voting and hierarchical discussion. It also provides aggregation (ability to see a feed of all your communities) and discoverability. Individual forums get you some way, but don't solve the aggregation thing (which is a primary way I use Reddit: scroll through my "Popular" feed). How about we just design some form of system that allowed people to build their own aggregated feed of a group of individually hosted forums? That would be (a) cool, and (b) we've just done federation.
