How can you get banned on 4chan, if they can only ban an IP address?

If you use a mobile network, e.g 3g or 4g, and you log off and on again, surly you regain access to posting 4chan? I change my IP address all the time, hence they can't ban me. Are people stupid enough to be banned from 4chan? Or should 4chan just stop the charade and stop banning people all together?