The Knols is a really new technology, and it can be a real threat to wikipedia. However, wikipedia is a great resource, and available completely free to us. The only difference it has from knols is that it does not pay its authors while knols has a system to pay its authors. It all can easily replace the encarta like encyclopedias. But according to me, google has to work with wikipedia, like acquiring it or so, rather than trying to exterminate it. And it will surely be tough battle for google.
LenX
http://www.lenxworld.blogspot.com