Well, if you search for Sheldon's Wikipedia article instead of following the
link you won't find it. That is because, apparently, Google has not made
most of the user added knol's publicly searchable. If you search for your
own while logged in, you'll see it - but no one else will. At least in the
early stages, it means a lot of people will create duplicate articles
unaware of what has already been written.
Nathan