you also have to worry that perhaps there aren't enough people in the world who actually want to write an encyclopedia to fuel Wikipedia, Citizendium, and Knol (among others).
Citizendium's small but not hurting for participants. They'll be fine.
That's not my point here. There is a certain number of people in this world who are going to be interested in actually "writing" an encyclopedia (as opposed to the people who are happy to edit, revise, or do other things to support the writing community). A lot of writers are already entrenched in these projects.
The one-author, one-page idea (from what I've heard knol is supposed to be) sounds like a disaster waiting to happen. Crackpot theories and all sorts of other nonsense that gets regularly edited out of Wikipedia is going to get pages in the top google-search ranks, that nobody can edit but the crackpot authors themselves. I can easily see, especially with no editorial control, that the signal-to-noise ratio is going to spiral downward rather quickly with this project. Wikipedia could end up becoming substantially more reliable in comparison.
--Andrew Whitworth