That's true - we've got members that haven't been around in a VERY long time, and would be thoroughly pissed to have their accounts deleted simply because they got bored of OP2, and decided to try out the rest of the world for a while.
I do that all the time with Diablo II. There's only so much you can do in that game and then not get bored with it. Especially after you reach the top, and essentially own 20 of every good item, and have one of every character build, even the odd ones. I got bored - so I quit for a few months, and return, and my gaming community has never once deleted my account. It's just a hearty, "CHRIS, you're back" all around.
I'd hate to come back to them one day and just have a 4k+ post count account be deleted and me have to start over...
I suggest we implement the system hacker mentioned. It'll PM the user, hence E-Mailing the user, which should get their attention if they have any interest in keeping up to date with OPU. I change my e-mail address all the time, but whether i'm active in Diablo II at the time or not, I notify that community so I can still recieve correspondence.
-Chris