I don't want anyone to take what I've said the wrong way. What I was trying to say is that, for the small percentage of players who DO just want to continuously grief a server, and completely destroy everything, perma-bans shouldn't be out of the question. After all, with the new(ish?) Minecraft client, you can list out as many servers as you please. If a ban is permanent, that player is likely going to drop Kreatious from that list, and move on to other griefable servers; however, if the ban says it's only for a day or two, they may just keep it on that list, and check back in later, and (assuming the new plugins have already been implemented to prevent what last occurred) find a NEW way to cause havoc and misfortune.
And BY NO MEANS should a perma-ban be anywhere near the player's first offense. It should be well after several other warnings and bans. Scenario: Griefer uses mass amounts of tnt/lava/fire etc to an extent that the auto-revert and/or Eve can't repair it. Player responds to mods with a terrible attitude, swearing, threatening, etc., and is banned for a day. That player comes online the next day and does the exact same thing. If this were to repeat, let's say, 4 or 5 times, with the same pattern, and that player shows no sign of changing his or her behavior, THEN I would say a perma-ban may be the only logical option. (Purely hypothetical, but 100% plausible.)
This ensures that Zerg's intentions, of no player feeling like they're walking on thin ice, is upheld for conscious players. You really have to be TRYING to be permanently banned, in order to be permanently banned. This really leaves no room for being permanently banned by mistake.
Of course, even assuming a player feels he or she does not deserve to be permanently banned, he or she can still always appeal their ban. Although actions that should warrant a permanent ban likely leave little room for excuses, there is still always the option to do so.
Forgive me if it seems like I'm trying to put anyone's ideas down. I'm just providing my own input to help Kreatious be the best server it can be. I totally agree that temporary bans USUALLY get the job done; this is just my view on the small percentage of players that temp bans DON'T work for.