At the discretion of the author, a knol may include ads. If an author chooses to include ads, Google will provide the author with substantial revenue share from the proceeds of those ads.
Is this another setback to dead-trees media? If authors have a substantial revenue share on a knols page, they might even consider writing for the web.
One thing i’m sure: authors have earned their recognition as the most important source of knowledge, and if they choose to abandon the academic walled gardens, then Google will be one step closer to “organize the world’s information and make it universally accessible and useful“.