Telegraph: Mark Zuckerberg is now worth a record $47.1 billion, more than four times richer than the second-richest person in the United States under the age of 40. The Facebook founder took top place on Forbes magazine’s list of the 40 most successful young entrepreneurs in the U.S. after another record year for the social networking website. More than 1 billion people now use Facebook each day, viewing videos more than 8 billion times daily.