As CEO of Facebook, Mark Zuckerberg forced everyone's hidden friend lists into public view. As a user of Google Plus, Mark Zuckerberg just decided to hide his own friends. Double standard, much?
Zuckerberg used to top the rankings of popular Google Plus users. But not any more, because, out of apparent concern for his privacy, he's yanked from public view his list of followers and followees, the Google Plus equivalent of Facebook friends. This makes it impossible to gauge his popularity.
Of course, Google executives play by something of a double standard as well. By default, Google Plus makes your friend list public. But the people who run the service don't follow their own suggestion; five of six prominent Googlers tracked by SocialStatistics.com have opted to hide their friends, including social chief Vic Gundotra, CEO Larry Page and co-founder Sergey Brin.