You'd be surprised at some of the things that have gone down in the classifieds section. And yes, that includes some "want to buy" posts. While there isn't any way to make all transactions 100% scam proof (this is the internet after all), we feel that our modest rules go a long way to make the section as safe as possible for both buyers and sellers alike.I can't see why anyone placing a wanted would do it to scam anyone.
My uneducated guess would be that you need 50 posts to make use of the whole section, no matter whether it's for buying or selling.