Have you considered a short trial period (e.g. 1 month) to test it out? The section can always be pulled down if it fails to achieve its purpose.

I don't know how easy it is to personalise profiles on activeboard forums, but is it possible to have a business section that has to be subscribed to separately? You can set up a number of conditions before accepting new subscribers e.g. a certain level of membership (member? veteran?) and maybe make subscribing to it a two step process where the initial signing up is essentially for trial purposes and has to be reaffirmed. At least that way you'd be assured that those eligible for access to the section are long term members of Malawiana (which filters many of those who set up Malawiana profiles for purely disruptive purposes), and that members who are patient enough to complete the business section signing up process are more likely to have a genuine interest in the subject. This could even act as an incentive for members to increase their participation in discussions as they raise their membership status. On the other hand, the ease of access to Malawiana is attractive in itself. You might be making a sacrifice in restricting access to the business section.

You could also try a voting off system such as the type you get in chat-rooms. Disruptive individuals could have their access to the section barred for lengths of time that vary according to factors such as whether the individual is a frequent offender, etc.