Two quotes illustrate the difference in the two approaches

KNOL

Set the permissions for who can edit your knol.  By default, Moderated Collaboration is set (at the right).  This means that if someone suggests a change to the page, you must approve the change before it is made.  You can also disable collaboration entirely or make pages open to anyone who wishes to change them

WIKIPEDIA

If you don't want your writing to be edited mercilessly or redistributed for profit by others, do not submit it.

If you create a knol then you, the author can choose the degree to which other people can engage in editing that material.  On the other hand if you create a WIkipedia article then you must expect anyone to edit it without mercy.  In effect the constraint structure of a knol is imposed by the author while in the WIkipedia it is the communities' ongoing interpretation of the five pillars.  In Wikipedia even the help pages can be edited. 

Now you can see why some KM people would like this.  Most of what I called the Nonaka period in KM was based on the same principles as a knol.  A expert group create a document or set of documents, its published with other articles. The focus is on search and return of units.  Documents constrained by author, contrasted with free flowing text created by a community; rules v heuristics; control v self-organisation.  The major mistake of traditional KM was well meaning but excessive constraint which means you don't get evolution.  Lightly constrain the system, increase the diversity of connections and interesting things start to happen: meaning emerges. Of course that means that you have to trust the network of people who engage, and as most active wikipedians will tell you the crowd generally turns out to be wise (largely because of those light constraints).  Nonaka period KM was always worried about issues of validation, the essence of best practice.  Reality was and is, the day to day exchange of fine-granularity information objects (OK anecdotes but I wanted to make a point).  Goggle have in effect created a world wide KM system based on the principles of KM that were established in the final five years of the last century.  Now we know that didn't work.  Ron may be hoping that the volume of a world wide system may provide new hope, but from my perspective the constraints are too great.

Now I should confess here that I renamed an article by Ron in the Wikipedia on the 10th May this year (you can see why with the edit history) and I am happy to defend that decision.  The same article as a knol could be protected.  I think that rather makes the point.