You've probably heard Mark's name mentioned once or twice. He runs a little site called Facebook.
According to the social-website-crawling SocialStatistics.com, a site managed by The Next Web's Boris Veldhuijzen van Zanten, Zuckerberg is top of the pile with over 29,500 follows (and 68 friends). The three below him are all Googlers, including Google CEO Larry Page in the #2 slot, who doesn't even come close to the big Z with his 19,800+ followers (and, curiously, zero friends).
Google's fledgling social network, Google+ allows users to both friend and follow others. You friend folks by dumping them into various circles — your mother would go into one labeled "Family," for instance, or your buddies into "Buddies." Then you can choose what circles you share what with, though anyone can opt to follow you — even if you don't friend them — and receive your public updates.
In other words: it's like having a Facebook profile that people friend and a Facebook page (such as those used by actors, blogs and so on) that people like, but mashed together.
Of course, one always wonders, "Is that really Mark Zuckerberg?" According to Business Insider, it is: "And yes, we're pretty confident it's him, because that's a picture we haven't seen before, and most people in his 'circles' are Facebook execs."