Me myself have never been permanently banned, only have had my account banned for 24 hours maximum.
I feel no pity for the ones getting banned for example boting and such, since it destroys peoples gameplay, but having their account suspended for ever seems a bit lame. There are innocents who gets banned aswell!
I'd say Blizzard should make a "exiled"-realm for those who have been banned where there are no rules, and they cannot migrate or anything like that. Just play. And cheat. Like a prison but a realm. The name of this server should ofc be Azkaban!