Actually they can still IP ban. Rotondo did say he did it in the past with some gore spammers iirc
its pretty easy to circumvent ip bans. proxies are free and some are even within-browser these days.
really the $10 an account is the best way to deter people from doing stuff. im sure most people value their money over being able to stuffpost on a forum, esp when they realize they've spent $50 for just a few laughs by their fifth account. unfortunately it doesnt deter people who are willing to steal money like okiver