I think it is commendable to want to protect members from possible conmen but other than that, everyone is using the forum to their advantage, after all, it is meant for the members to benefit the members, nothing more, nothing less. That is the crux of all car clubs, a place where we can all share our interests, experience, get to know one another and if there are other benefits, even better.
In terms of the problem with commercial posts (why is it a problem in the first place?), perhaps it is advisable to charge a certain fee for other companies who wish to advertise, but use that fee to benefit the members as a whole eg. sponsor some road trips, subsidised club merchandise etc etc. I'm sure the club legal advisor can find out how to go round this. If a church can collect donations, I'm sure a club can also collect some fee to benefit the members. We just have make sure that it does not violate any regulations. Anyway, just my 2 cents opinion.