I honestly wonder if Muppetfan/Hubert has passed away or fallen into some dire circumstances.
Twice I've had friends who suddenly disappeared off the face of the internet.  One guy committed suicide, and the other I later found out had been committed to a mental hospital for bloody murder.

I'm not entirely sure, but the last I heard, somebody over at Muppet Central was in direct contact with him, and he said he needed to take a break from the internet in general, because of all the negativity (even though I'm not on the Wiki, I understand troll problems over there were a major contributing factor in his decision).

I think, too, things got real busy for him IRL, so he probably also didn't or doesn't have a whole lot of freetime to check on any of this stuff... that could be it, I'm not sure. Alls I know, for certain, is that he decided to take something of a sabbatacle from the internet.