The New York Times reports on Google's vision for Knol as a place where experts can share their knowledge on a variety of topics. It hopes to create a sort of online encyclopedia built from the contributions of scores of individuals. But while Wikipedia is collectively edited and ad-free, Knol contributors sign their articles and retain editing control over the content. They can choose to place ads, sold by Google, on their pages. While Knol is only three weeks old and still relatively obscure, it has already rekindled fears among some media companies that Google is increasingly becoming a competitor. They foresee Google's becoming a powerful rival that not only owns a growing number of content properties, including YouTube, the top online video site, and Blogger, a leading blogging service, but also holds the keys to directing users around the Web.