I believe that if individual forums sprout individual gathers that there is no harm, no foul. If Randy requires they be cross-posted to CommunityBuzz in one fashion or another, I'm okay with that (were I in Randy's shoes, I don't know that I'd require it).
The exception to this would be if the discussion of gatherings and DOs and such started to overwhelm or overshadow the original purpose of the forum in question, at which point I believe the discussion should probably move to CommunityBuzz.