According to Jason Stone on today's MMO Report, he's designed this very elaborate "prison system" that is AoC's take on anti-griefing, and it will be implemented fairly soon because it's essentially done and was part of the "launch plan" for the game.
In essence, it specifically targets griefers with a "bounty system" coupled with a "prison sentence".
Griefing would essentially be repeat kills of a player that provides no challenge. For example, repeatedly killing a player much lower level than you who has no chance at all to win against you (so some type of level differential). It would also encompass something like too many successive kills in a row or timeframe (I'm reading between the lines of what he actually said here).
So say you do this in Cimmeria. Enough offenses and you get a "Cimmerian bounty" placed on you. The Bounty Hunter NPCs in Cimmeria can then somehow capture you (no details here), so you can choose to flee to Aquilonia or Stygia and do your dirty deeds there instead. If you ever come back to Cimmeria, you will still have a bounty on your head (no time-out, apparently).
If you get caught by the bounty hunters, you can either bribe them to let you go by paying some amount above and beyond the bounty (one type of money sink penalty), or you can choose to serve prison time.
The prison time is meant to be actively unpleasant. You can't just wait it out. You must perform menial, boring tasks such as "take this stick and kill 300 rats" or "carry this stone to the other side of the yard, pick up a stone on that side and carry it back, do this 300 times", etc.
Finally, somehow the "prison" is visible to other players, so that you get the embarrassment of being seen serving your prison time and doing those menial quests.
..and their unique anti-greifing prison system that will be folding into the game soon after launch..