I've not tried Snog's solutions, but I agree with Alfa's assesment of Nobita's add on.
The solution is there needs to be a rock solid feature rich an extensible groups/clubs feature in XF core.
Users want it, admins want it and it drives activity. Let site admins get those page impressions and offload some of the forum moderation work to group admins before Facebook starts letting group admins monetise. They let news publishers monetise in the past, then ditched them when that didn't work. However groups are thriving, big time. It takes work to administer a group though, they've been slowing adding more features to groups and I predict it's only a matter of time before Facebook starts revenue sharing with facebook group admins in order to keep them alive, thriving, and on the platform.
Those same people are potential forum admins, getting swept up and tied to the facebook ecosystem. They'll grow their groups faster than many forums due to the one click join functionality of a billion user ecosystem, then once they reach a certain threshold it'll only take a click of a button before facebook starts putting money in their pocket. No messing around with adsense or figuring out the best place to put banner ads. Facebook will take care of all of that, the admin just needs to focus on the users and the content, ensuring continued activity.