We have had this discussion before.
Some people innocently post "For Sale" ads here because they don't know any better and other similar forums allow it.
They are usually self-policed very quickly and the some of them even apologize.
Rick deletes the thread when he gets the chance.
Some jerks know better and do it anyway.
The "Catch 22" is the sailing industry professionals.
Do we make Bill Roberts stop mentioning the advantages of his type of designs, the Supercat, SC and ARC family?
Do we stop Bill Curry from explaining good sail design?
Do we stop Mark from answering the frequent "Where can I find...." questions?
There can't be a simple rule which covers every situation.
I think forum is doing just fine.

But then you know how easy going I am :-)