It is not an exaggeration to suggest that If I - liberal arts graduate focusing on technology in academia - had not found _why's guide, I would never have believed I had a mind capable of doing code professionally. I will be celebrating my 10th year in the industry soon.
My understanding is that he burned out and had to take himself offline. He used to be involved in quite a bit (also see Hackety Hack), and it can be really exhausting for some people. I'm hopeful that he found the balance that he needed, and glad for all the contributions he made along the way.
My understanding is that his "true identity" got outed and he disappeared off the scene after that.
Imagine! The guy was both an insanely productive programmer and Ruby evangelist. He gave more to the community than anyone could repay. And what did he ask for in return? He asked to be the Lone Ranger.
All he wanted was anonymity. He wanted to be the masked hero who rides in, does a bunch of good, and then gallops off before anyone has had a chance to thank him. He was an eccentric, a romantic. That romantic eccentric was a benefactor who asked basically nothing in return.
And some nobody decided it would be fun to pull off the mask. Who was that? We'd have to look him up to know his name. He ruined it for _why and for the rest of the Ruby community. Why? What for?
It's not so much that I'm sad that _why is gone, as that I'm sad that there aren't more people like him. We went from having one _why-like force in programming to having zero. And that is the shame.