Before Wikipedia, people like this author predicted it would be impossible. Science fiction authors wrote about it, but understood it to be fictional—Asimov showed how a great encyclopedia contained the seeds of its own project failure. Adams meant it as a joke.

And attempts like everything2 and h2g2 were neat art but nothing like Wikipedia. The spinoff attempts to do something like Wikipedia also failed.

This is characteristic of something that is probability zero in its particulars but rather likely as an example of a class.