The article is flawed, but his profile still doesn't seem to play by the rules. When I go to facebook.com/zuck there is no option for me to request adding him as a friend. In normal privacy settings you can specific that either everyone can add you as a friend or only friends of friends. I have two mutual friends with Mark Zuckerberg.
So either his profile has some additional privacy setting (i.e., to only send out, not receive, friend requests) or something else is at play (like he has hit the friend limit -- I'm not sure what that looks like, to be honest).
"In normal privacy settings you can specific that either everyone can add you as a friend or only friends of friends."
There was a big privacy setting change last October that you could opt out of. So it is theoretically possible that he did. (I wish I had. I didn't understand the ramifications at the time.)
Obviously, if this is in fact the case, it is still a case of Zuckerberg not playing by the rules he is setting for everyone else.
Or all he's other updates have been friends only. It wouldn't surprise me if he has now recently opened his own account up more in a sign of support for the new settings.
Not his profile: http://www.facebook.com/zuck