The time is ripe for something like Knol to be re-introduced.

Even before Knol, we had something like this, and they were called personal websites. People would use them to document their passions (or anything, really) and you could find them on Google. People are probably so addicted to centralization and services, though, and Google's approach to ranking so overwhelmingly works against that style now, that it's probably unworkable to argue for relying on that again.

Actually it is mostly selected by person rather than content or style. Mostly evidenced by the fact that accepted edits are mostly done by the same people. This is at least true for the German Wikipedia, but I have no doubt that the English one isn't any different.