Maybe you should have to be a contributor ($$$) to the site to post ads... Anyone can read them but only members can post.
On the forum where I spend the bulk of my internet time, the rule is only subscribed get to post in classifieds. The ads there are always worth reading for that reason and real--Unlike Craigslist where an awful lot of what is posted is worth about what they paid to post. NWFirearms can pick a path between those two.