I always thought that instead of banning people, it would be great if forums had a "Thunderdome" area that unruly members could be banished to. Make it private and unsearchable so that it doesn't effect the rest of the forum. That way people can spiral until they get it out of their system. After a certain amount of time of them not posting in the Thunderdome they could be let back into "polite society". Could even have a jury system to allow or deny someone being let out of the Thunderdome.