He's still around, but very busy. New job last couple of years which involves some pretty hefty shifts, among other demands on his time. Not gone, but for now less time available.
I've been around TFL since 2007, and seen a huge membership churn in all those years. Same for pretty much any forum I've ever been on really. People have come and gone for all sorts of reasons. One or two we lost because of the behaviour of others, some have had to be shown the door, one went off in a huff because they didn't feel appreciated, others simply lose interest in the 'vintage' scene and may or may not crop up on facebook snidely laughing at it all in future. Just how it goes with any interest group, really.
I think the only website I've stuck with as long as this is Facebook. Difference is, if something came along that replaced facebook with the same functionality but a much nicer place all round, I'd be gone from Zuckerberg's planet like a shot.