I think they are, I was just thinking the other day when reading posts from ex Zillion members who claim to be more than regular posters on Zillions boards blaming the reason why Zillion died was because not enough advertising. That might be correct but Im sure the MB had plenty to do with it. It was dead. I would pop in there from time to time and see the same 12 or 15 posters on the mb, all cosy up in their meaningless group not really being friendly to outsiders. It was like if your not in our group your not welcome type of thing. Now they're complaining why Zillion went down the gurglar and fail to see they were part of the reason of Zillions destruction! :)
I bet if TM did a survey asking members if they think the MB is important for the site you would get an overwhelming response of a yes. Of course TM would still soldier on without the MB being how big it is but for small auction sites starting up they need to push the MB as well. If people come to chat they will browse the site looking at goods from time to time.