Perhaps a useful tip for the forum:
I got this idea from this website.
Banning a user locks down a user's account and/or ip address. The user gets notified he's banned and may try another method of getting access.
An hellban is when a user still has access to the system, but the system totally ignores him. He can make posts, but nobody sees them. He thinks he can use all the functionality, but nothing happens. Basically all his actions are totally useless eventually leading to him leaving forever, because nobody responds. He doesn't even know he's hellbanned.
A hellbanned user is invisible to all other users, but crucially, not himself. From their perspective, they are participating normally in the community but nobody ever responds to them. They can no longer disrupt the community because they are effectively a ghost. It's a clever way of enforcing the "don't feed the troll" rule in the community. When nothing they post ever gets a response, a hellbanned user is likely to get bored or frustrated and leave.
I'm not sure vbulletin offers this kind of feature, but maybe if does it might mean less work for moderators and far more effective. The psychological impact of someone who finds out they've been hellbanned may be a lot worse though.
There are also other forms of banning.