What I would suggest that you do Corm ..
Create a commercial folder and charge people to post in it. Say £30 one off payment for the first 3 months and then £10 a month thereafter, if they wish to continue with their thread in the commercial folder. This will allow folk to have links in their signatures and no-one can cry spam, because they are paying for the privelidge. If they dont want to continue after 3 months then they lose the right to refer to their own site in any way through this site.
The money could be used to run the site and sponsor competitions or pay for a really good days out for members, at a race course, like Kelso or Perth for example.
I think we need a ‘bloggers’ folder and a ‘commercial’ folder, both are legitimate activities and should be catered for, IMO.