We only ban established members when there is a real need for it such as constantly breaking the rules, I am not sure if it displays but there is a user group called suspended when a member has earned a vacation, that is normally our final warning as it ware.
Of late we have had a fair number of cookie suffers show up, what happens is they post a smile from a site that will write a "Referral cookie" like the crucial ones (non so far have used crucial I am just using them as a example) they try an make them selfs useful to ensure that the cookies get lots of exposure, when we find them they get insta banned just like any other kind of spam.