I think this has been beaten to death on both sites, but I'll try to summarize here.
We are in possession of the database and own the contents of it. If we wanted to, we could read anything and everything in it.
But, we don't want to. There are far more important things that always need doing, and really, what would be the motivation?
From a technical viewpoint, the messages themselves can't be read using direct access to the database. The type of field they're stored in doesn't display when accessing the database directly. They have to be fetched from the database and formatted for display.
No such routines exist on either site aside from the ones we all use. Matt and I have no routines available to us (I could write one but have no reason or desire to) to let us read messages not from or to us. In most regards, the site sees us as it does any other user with the exception of a few management links.
Your PM's here are no more or less "secure" than your emails. You send someone an email, they can send it to someone else. And people at your ISP can, if they want to, read your emails. PM's do have advantages over emails in that they're web-based (accessible from anywhere) and virus-proof, but they're no more "secure" in any other regard. Oh, and they're largely spam-proof.
The only way either of us can read someone else's mail (assuming it's not addressed to us) is to log in as that person. That's easy to do. It take seconds to look up login info.
But we don't do that unless we need to and are given permission. And for my own part (Matt likely does the same or should), I ask for permission and a specific URL so I can only look at the PM I need to see, then get out of the account.
Actually, most of the time that someone wants me to log into their account, it's been because they've done something bad in their personalized setup (like setting foreground and background to the same color), but I've since figured out how to check for this without logging in as them to find and fix it.
So, the short answer is: Yes, we can definitely read your PM's if we want to badly enough. No, we definitely do not read them. Should we?
Betcha I see a short, out-of-context quote from this message on RB soon. <g>
