Essentially with Knol having a commercial bias there will be a tendency for the system to reward popular articles. This will be in much the same way that, say, the music industry enormously rewards a handful of "stars" despite the obvious existence of hundreds of equally or even more talented musicians who are rewarded much less (if at all) by the industry; the system is biased to promote what it knows has been and therefore assumes will be successful.
So will Knol be good or bad? Has Google slipped in to "being evil"? It all depends on where you stand and how you view the issues. Tim O'Reilly commented: "Everyone applauds when Google goes after Microsoft's Office monopoly, seeing it simply as 'turnabout's fair play,' (and a distant underdog to boot), but when they start to go after Web nonprofits like Wikipedia, you see where the ineluctable logic leads. As Google's growth slows, as inevitably it will, it will need to consume more and more of the Web ecosystem, trading against its former suppliers, rather than distributing attention to them. We already take for granted that common searches, such as for weather or stock prices, are satisfied directly on the search screen. Where does that process stop? And much as I support what Google is doing with Google Book Search, I am troubled by the fact that they give preference to their own content repository over digital copies provided by publishers or other aggregators."
The fact is that if Google hadn't done Knol then Yahoo or Microsoft or some other powerful player would most likely have done something similar. Sure, Google was the most well-positioned, but where there's a commercial vacuum there's always something that is ready to fill it.
Knol was a foregone consequence of the market. Now we'll just have to wait and see how well the contributors of Wikipedia hang in there and just how good an idea Knol really is.