If the forum is popular it will attract spammers - if not via signature campaigns then by shitbumping and other activities. Arguably the cost of entry into the hallowed ground of signature spamming is already quite high - you need 100 merits to be able to carry a signature that's worth something. At one point a lot more high-rank users were being banned than new ones were ranking up. Not sure if that's still true but there was and still is a lot of effort being put into cleaning it up so calling signature spam "worse the [sic] ever" is probably incorrect.