Message boards were already getting to be old fashioned when younger millennials were coming of age. It would not surprise me at all if > 50% of the active board members were Gen X or older (let's say only counting users averaging at least 1 post per day over the last month or something, for example). I would guess one of those generations has the plurality on their own, but I'm less confident in that.
NandoNet
"One POSSIBLE future. From your point of view... I don't know tech stuff.".... Kyle Reese