Google’s Knol service is being billed as a Wikipedia killer, and while it has its similarities in purpose it has differences in implementation that set it apart. First of all, the Knols (individual units of knowledge) are not as open as Wikipedia. Individuals can collaborate in groups but you can also make control your own knol and be its sole contributor.
In practice this means that there can be many Knol articles about the same subject and this will mean less consolidation and more diversity. The mission statements are very different as well, and you don’t need to write with a neutral point of view on a Knol and can produce original research. You can probably post a lot of pure garbage that wouldn’t be allowed on Wikipedia on a Knol.
The effect that I predict that this will have is that Knols will be more like individual web pages than a Web Encyclopedia. And they are going to tend to be more commercial and less academic without the encyclopedic purpose and with the revenue sharing of Adsense ads that they will offer their contributors.
Expect a SEO heavy crowd in the early stages. This is going to be more like blogging that Wikipedia in effect.