It's happend

[SeanGAR]

Originally Posted by architeuthis

As far as how vBulletin is set up, the only way a moderator or admin can read your PM's is to switch user id's and log in as you. Yes the owner and admins can do this, but truly do you think they really have the time? The work involved in this changeover they are doing probably keeps them working 20 hour days...

I don't think so, looks like a simple hack to me which the site owner/super administrator can easily add.

From the link (date Jan 2009):
This allows a super admin to read the private messages (all folders) from any registered member through the admin control panel.

http://www.vbulletin.org/forum/showthread.php?t=92815

And I don't think they would read all messages ... maybe just those from "esteemed" members. Whether or not PMs were noticed from bounceback or the hack is unclear. I know where I'd place my bet ....