One of Zuckerberg's dorm-mates and a Facebook co-founder, Hughes was charged with promoting and speaking on behalf of the social networking site in its earliest days.
Later, he moved on to helping Barack Obama's campaign galvanize supporters online.
Hughes' most recent venture is Jumo, a social network for non-profit groups that will launch later this year.
Another Facebook co-founder who has been with Zuckerberg since Facebook's early dorm-room days, Moskowitz is also a young billionaire thanks to the social networking giant.
He was Facebook's first CTO and stayed with the company until 2008. In that year, he left to start a software company called Asana that helps individuals and small businesses with collaboration.
According to Forbes, he is the 290th richest American, with a net worth of $1.4 billion.
A co-founder of Napster, Sean Parker is ever the entrepreneur.
Aside from Facebook and Napster, Parker helped launch Causes, a Facebook application to help organize charitable giving, and now is a managing partner at the Founders Fund, a venture fund.
The founding president of Facebook, he left the company after a cocaine arrest, though charges never were filed.
According to a recent Vanity Fair article about the 30-year-old, true to the movie, he's known for a penchant to party and is worth about $1 billion, thanks to his share in Facebook.
These Olympic rowers drive much of the drama in "The Social Network." Along with their Harvard classmate, Divya Narender, they contend that Zuckerberg stole their idea for a social network based at Harvard.
Claiming that Zuckerberg used their code for their social network -- Harvard Connection and later ConnectU -- the brawny blond twins sued Facebook and received a reported $65 million in a settlement.
Currently, the "Winklevi," as they are referred to in the movie, are pursuing MBAs at Oxford University.
At a recent screening of "The Social Network" in New York, Cameron Winklevoss told the New York Daily News, "The film is nonfiction. ... Mark Zuckerberg seems to be the only person in the world capable of commenting on the veracity of a film he has not seen. 'Clairvoyant' should be added to his business card."