since we're talking about the classifieds rule, I do want to say I somewhat agree with it.
I've thought of implementing a similar rule on a small forum I run (it'd be more like 5 or 10 posts).
As a forum admin, especially because mine is a local riders forum, I feel responsible for what goes on and rules like that keep scammers out of forums and therefore keep my members from having their hard earned money taken from them. Similar to having a captcha and account activation by e-mail, it is a bit of an inconvenience but it keeps people from getting screwed over.
I also view a classified section as a benefit for the users so it can be annoying to see someone join the board, never add anything to the content of the site, but take advantage of the deals that are intended for people that contribute.