Here is a concept for a forum moderated by money:

Each post costs a small fee (paid to a community reward pool)
Replies cost a small fee (paid to a community reward pool)
Upvotes cost a small fee (paid to the poster)
Post visibility/ranking is determined by sum of community investment (total money spent on the post from all users) -- halved every x hours so as to keep things fresh.
Community reward pool divided among most "valuable" users (valuable might be users who post things that get most upvotes or users who spend money to upvote things that others go on to upvote, etc)

Reputation could also be added to this, weighting the money spent by trusted users more than untrusted or new users. But the idea is that associating a cost with forum actions might make them harder to game and relieve the burden on moderators).

What do you think of this idea? Where could it fail or cause friction? What dynamics might be interesting to add?