One of the more interesting technical approaches I've heard about for dealing with trolls is to send them into
The Phantom Zone. The Phantom Zone is just a hidden forum database that mirrors the real one.
People identified as trolls are automatically routed to the Phantom Zone forum. From there, they can read all the real mirrored postings. They can also troll and flame to their hearts content. But nobody on the real forum ever sees what the troll has posted. He has ceased to exist. But from the troll's perspective
nothing is any different. He thinks he's still in the real forum. This is the key to why it works. If it were otherwise, the troll could just register under a new name and resume causing trouble.
Eventually the troll gets tired of being 'ignored' and wanders off to annoy somebody else after posting a few dozen rants that nobody will ever read or respond to.
Hasta la vista, Baby! The Phantom Zone - It's a beautiful thing!
BTW: Some particularly crotchety forum operators have been known to add additional wrinkles to the Phantom Zone concept. Common tweaks include: slowing down server response times; randomly mangling part or all of the troll's postings; faux timeouts and lockups; bogus "Forum Down for Maintenance - Please try us again later." messages, etc.
Possibly cathartic, but IMHO hardly worth the effort.