Google VP of Engineering Udi Manber's pre-announcement details just what the hell a "knol" is. They apparently wanted to copy a wiki, but brand it with their own term.
Right now, it's invite-only, and apparently you have to be the wife of a Google VP to get an invite, but it seems like it will be yet another spammers delight (a la Google base, two years ago).
Manber does seem rather selective about who should write a knol:
Our goal is to encourage people who know a particular subject to write an authoritative article about it. The tool is still in development and this is just the first phase of testing. For now, using it is by invitation only.
Can't wait to see those first knols on Ringtones, Viagra, and Online Poker. I wonder if Google is actually too late to the party with this? To me Google Base was late to the classifieds party, and hasn't really taken off. Will the real experts really have incentive to do a knol, rather than contribute to wikipedia.
I guess if Google starts to demote those Wikipedia entries, they might.