Mark Zuckerberg is on Google Plus
|Clicking the picture will take you|
to Mark's Google Plus Page
While scouring the web for people with Google Plus Invitations to spare, I found Danny Sullivan, who wrote about Jenny Lee, who tweeted about finding Mark Zuckerberg's Google Plus Profile.
Don't know if it's legit though. :)
Update: It appears that this is really Mark Zuckerberg based on the people in his Google Plus Circle:
1. Ben Barry - Related to Mark Z. in some way
5. Joshua Pritchard - One of two inventors who filed a patent application in behalf of facebook for "systems and methods for classified advertising in an authenticated web-based social network"