Exit addresses (first described here) are defined as follows: "When you create an account with a site, you should be able to enter an address that, should anything go wrong, your coins will be sent to. Deepbit, for example has an option that will let you 'lock your payments address forever' meaning, even if someone hijacks your account, they won't be able to withdraw money anywhere."
Many members of the bitcoin community have advocated that any service accepting bitcoin deposits (as opposed to payments -- i.e. exchanges, etc) ought to include an exit address facility, and allow enactment of exit address policy at any time. This would avoid the conflict of interest inherent in "anti-money-laundering" account freezures, whereby the exchange actually books a profit under accepted accounting practices as a result of balances inheriting from accounts abandoned in response to account freezure (once the statue of limitations on embezzlement expires).