How to tell someone is here for a "quick fix"

There should be some kind of agreement during signup that the person will make, say, 10 posts in 2 weeks to "perm" their account. That's not even 1 post per day. That would eliminate these 1 or 2 post accounts from hanging around. Also, if you only went through and deleted any accounts with less than 5 posts you wouldn't be deleting anyone's account that would be coming back.