As you say, FF has implimented this idea, Commercial members (or vendors) are simply not allowed to post in the main forum.
They are restricted to posting in a sewer, where literally anything goes. Spammers, Ponzi operators, scammers and legitimate vendors all share the same space.
I didnt think this would work, for the same reasons that T2W management and staff always give, and that is, you'd lose good input from legitimate vendors. I was wrong though, it has worked at FF. The main threads are clean, and the vendor sewer has pretty much died a death, other than for some vendor bashing, and the "legitimate vendors" simply havnt been missed at all.
The long standing "legitimate" vendors didnt stay and provide quality input in the sewer, they fled to forums where their "input" is valued.
I have no idea if there been an increase in the traffic generated after the implimentation of the "sewer", and I'm no great fan of FF, its far to gay a forum, but I think the quality of contributions has improved now its a vendor free zone.
It wont happen at T2W,99% of contributors are vendors (although you wouldnt know it since they did away with the vendor tag ?)
Edited to add, vendor tag is now back ! well done T2W