If I say "Facebook," you think Mark Zuckerberg.
In reality, it's much more complicated than that, as you probably know if you've seen Facebook's slightly fictional origin story, 'The Social Network." Zuckerberg wasn't even the company's first spokesperson.
The five founders were classmates at Harvard College. Zuckerberg, who was the mastermind* behind thefacebook.com as the site was called at the time, recruited roommates Moskovitz and Hughes, and two other friends to help him develop it.
Zuckerberg had known Eduardo Saverin for about a year when he invited him to join. Saverin was Facebook's first investor and took on the business partner role in the relationship during the early stages of Facebook.
Moskovitz, keen on helping Zuckerberg expand the site, learned the PHP language in "a couple of days," according to Zuckerberg, and became the company's first CTO. Hughes served as the spokesman, beta tester, PR specialist, customer service representative, and everything else user-facing, but he didn't write code or handle any of the business.
Zuckerberg knew Andrew McCollum from all of their computer-science classes, and he asked him to design Facebook's first logo — a face that was actually a sketch of actor Al Pacino. McCollum also worked on Facebook's file-sharing program called Wirehog, which never took off the way Zuckerberg planned.
The summer after the site launched in 2004, Zuckerberg, Hughes, and Moskovitz traveled to Palo Alto, California. Zuckerberg and Moskovitz decided to drop out of Harvard and stay to relocate their operations and start hiring employees. Hughes went back when the semester started, but joined them again when he graduated in 2006.
While they were in Palo Alto, Zuckerberg pushed Saverin out, and diluted his shares to 10% because of what Zuckerberg believed to be Saverin's lack of contribution to the company.
Saverin eventually sued Facebook over breach of fiduciary duty. He walked away with 4% of the company, and today he lives in Singapore, having renounced his US citizenship in 2011 — a year before Facebook's IPO, meaning the taxes he had to pay on capital gains were significantly reduced.
McCollum left in 2006, and co-founded the online preparation tool JobSpice. He's the current CEO of internet television company Philo and acts as Entrepreneur in Residence at both New Enterprise Associates and Flybridge Capital Partners venture firms.
Hughes left Facebook in 2007 to volunteer for Barack Obama's presidential campaign, did non-profit work with Jumo and UNAIDS, and purchased a stake in "The New Republic" magazine, which he later sold. He made $500 million when Facebook went public, and recently wrote a book called "The Fair Shot: Rethinking Inequality and How We Earn," citing his own wealth, most of which stemmed from his 2% ownership in Facebook.
Moskovitz left in 2008 to co-found team management app Asana. He continues to be the CEO there, as well as the co-founder of the philanthropy Good Ventures and an angel investor. He owns a 7.6% stake in Facebook, and was the youngest self-made billionaire in 2011 since he's 8 days younger than Zuckerberg. He and Zuckerberg both joined The Giving Pledge, started by Warren Buffett and Bill Gates, to give away at least half their wealth to charity.
*Shortly after the site launched, Cameron and Tyler Winklevoss and Divya Narendra — Harvard seniors at the time thefacebook.com started — claimed they had asked Zuckerberg to create a similar site for them, and they sued the newly incorporated Facebook and Zuckerberg. They settled in 2008.