Mark Zuckerberg shocked at success
Facebook founder Mark Zuckerberg told the NBC Today Show that he never thought he would "be a part of something like this" as the site hit one billion users.
The Facebook billion: An internet milestone is crossed
Facebook's milestone has social, cultural and financial implications.
Zuckerberg 'proud' as Facebook hits one billion users
The social networking site Facebook has more than one billion users, founder Mark Zuckerberg announced on the site.