I guess pretty much everyone in the blogger world has already posted about Knol, but I’ll add my two cents in as well.
Ever since Knol was announced, people have seen it as a direct rival of Wikipedia. However, it uses quite a different “business model”, and way of operating. While Wikipedia uses a model where each topic has one article (don’t nitpick, I’m going somewhere with this), and people must collaborate to find the best way of representing the topic to the audience, Knol uses a very different approach, where there can be an unlimited amount of articles about the same topic, and where each article has one author. The authors may choose to open their article to collaborative editing by others, but they are always in control.
Knol’s approach is totally different from that of Wikipedia, and I believe the two projects fill different niches. Wikipedia is the place people will go to find a neutral article about a subject, while Knol is where they will go to gather different opinions about the subject.
I also believe Knol attracts a different kind of contributors than what Wikipedia does. Since Knol bases articles on author ownership, it will probably attract the kind of authors who like their names to be published, like professors who would never write on Wikipedia for a multitude of reasons. This is a very good thing, because this makes their knowledge available and accessible to people who would otherwise never be able too; and since Knol uses free license as its default license, this may just make the world a better place.
However, one of the drawbacks of Knol’s one-author-one-article approach is that it will also attract people with strong points of view, who will write very biased articles about controversial topics (or even not-so-controversial topics). But I see that Knol has a rating system in place, and hopefully this will mute the very extremist articles. But hey, maybe this will lead those POV-pushers away from Wikipedia, and stop bothering us?