A hacker could get access to your account then edit all your posts where you posted an address, and delete all your PMs, and change email. Account not recoverable, unless you have the secret question.
He wouldn't be able to delete and edit posts made in the Auctions child-board, and deleting a PM from the Outbox doesn't make it magically disappear from the recipient's Inbox (and there are forum backups, too).
As malevolent said, the PM won't be deleted if one person deletes it.
It will be deleted if both people delete it and though they are backups, they most likely will not be checked for a single person.
Theymos has said in the past that you should send a PM to an account that will never delete it.
I recommend sending it to DefaultTrust and then saving the PM id.
In case someone is wondering, here is the post theymos mentioned that.
https://bitcointalksearch.org/topic/m.7169449
It's best to include it naturally in a post. But if you can't, you can send a PM to an account that won't delete it (you could use DefaultTrust for this). After you send it, check your outbox and make a note of the PM's ID (visible in the quote URL).
