I've been concerned as well. I sent him a PM ~a month ago asking if all was well, but never heard back. I don't have his email though so not sure if it is a case of just not being on interact. He is surely missed though; by far the most knowledgeable person on the forum, and he has personally helped me out a ton.
Edit: didn't realize there was already a post about him--I don't ever check that board.
I do have his email, and I've emailed it, but still no response.
At one point I had his actual physical mailing address. He sent me something once, but I discarded the box and don't have it anymore. If I did, I'd consider actually sending a letter, since if something seriously bad happened, that might generate a response from whomever is handling his accounts (where they might not be able to get into his email, or might not really bother to respond to "some dude" from the Internet).
But alas... I looked, and can't find it anywhere.
I also got a little bit creepy and tried to look up obituaries and stuff, but I don't know exactly where he lives, so it was next-to-impossible to look.
Hopefully he's just been crazy busy or something. Or maybe on some kind of super-secret project where he can't discuss anything with the outside world (secret aaaagent man). Dunno. If he is on a walkabout, it has been a
long one now.