A jerk who was pissed about the editing rules started vandalizing content en mass. It seems Ward got tired of battling him/her/it and switched on some kind of serverless or distributed version of the wiki that he had been working on as an alleged alternative. Most find it baffling and/or unusable. That effectively killed the wiki, at least to new authoring. Maybe after Ward realizes it's a flop, he'll go back to something more familiar. (It might have other uses, just not as a public wiki or discussion board.)

Ward Cunningham is considered the inventor of wikis, by the way.

I just navigated to the link directly, and everything seems fine.

http://wiki.c2.com/?EverythingIsa

It's all read-only now. Changes are no longer allowed, at least not as seen there.

They took a perfectly good website and rewritten it as an SPA.