Is the restricted scope generally typical of FB? The above all have specific fields of interest unlike this or other forums. Is there anything with unrestricted cover? As Richard notes above, there are a few well known names about, but if the scope is limited, then it seems a wasted opportunity.
Realistically, when dealing with more knowledgeable minds, you would probably be better speaking at a fair, phoning or emailing, which trumps any forum/group discussion which tend to have short posts because many people can't be bothered formulating or reading lengthy replies. From a personal perspective, I regularly end up discussing a query for anything from 10 minutes to an hour because few things are that straightforward.