I know the forum administration could change the advertising forums to require 25 regular posts before you can even post in those forums. There is that option.. If you want more substance, it could do something to add more posts.
I know WHT uses this method.
There used to be a mod that allowed you to post a in a forum every x days if you are part of a certain member group. Don't know if the mod is still in production.
Options are already available.
limit private messages till after 10 posts.
Seriously instead of whining about something, suggest solutions.