NEW YORK | Before 2010, Mark Zuckerberg, the 26-year-old co-founder and CEO of Facebook, was primarily known as a mysterious, sweatshirted figure, a Silicon Valley wunderkind familiar mainly to those in tech circles.
But this year, Mr. Zuckerberg has been thrust into pop culture ubiquity, appearing on screens of all shapes and sizes, from "Oprah" to one of the year's most acclaimed films.
On Wednesday, his public ascent was solidified by Time magazine, which named him its "Person of the Year." He's the youngest choice for the honor since the first one chosen, Charles Lindbergh in 1927.
In a posting - where else? - on his Facebook page, Mr. Zuckerberg said being named Time's "Person of the Year" was "a real honor and recognition of how our little team is building something that hundreds of millions of people want to use to make the world more open and connected. I'm happy to be a part of that."
It caps a remarkable year for Mr. Zuckerberg and Facebook, which has more than 500 million users worldwide and market valuations that go into double-digit billions. In countless redesigns and new features, Facebook has been pushing toward becoming not just a social media hangout, but also the underlying, connecting fabric of the Internet.
Time, which many expected to choose the news-making WikiLeaks founder Julian Assange for "Person of the Year," cited Mr. Zuckerberg "for changing how we all live our lives."
"I'm trying to make the world a more open place," Mr. Zuckerberg says in the "bio" line of his own Facebook page.
Mr. Zuckerberg was perhaps prompted to expand his public persona because others were doing it for him. "The Social Network," director David Fincher and writer Aaron Sorkin's acclaimed drama of the contentious creation of Facebook, has supplied an unflattering narrative to him and Facebook.
The film depicts Mr. Zuckerberg (played by Jesse Eisenberg) as a brilliant, power-hungry, back-stabbing hacker motivated by social acceptance and girls. Facebook has called the film (which Mr. Sorkin wrote based partly on Ben Mezrich's book "The Accidental Billionaires" and without Mr. Zuckerberg's cooperation) "fiction."
But that hasn't stopped it from becoming a sensation with critics and moviegoers, and arguably the most talked-about film of the year. It has established itself as an Academy Award front-runner, which is sure to keep the film in the news until the Feb. 27 Academy Awards.
Mr. Zuckerberg countered the release of the film with a $100 million donation over five years to the Newark, N.J., school system. He appeared on "The Oprah Winfrey Show" to announce the donation. He's in the company of media titans Carl Icahn, Barry Diller and others who have joined Giving Pledge, an effort led by Microsoft founder Bill Gates and investor Warren Buffett to commit the country's wealthiest people to step up their charitable donations.
But Facebook touches the lives of an enormous audience unimaginable to any Hollywood film. Mr. Zuckerberg, who grew up in the New York City suburb of Dobbs Ferry, the son of a computer-obsessed dentist, has built Facebook from a dorm-room creation at Harvard into the largest social-networking site in the world.
As it grew, he steadily turned down offers from companies like Yahoo and Microsoft, and has so far declined to take Facebook public. Asked about a Facebook IPO on "60 Minutes," Mr. Zuckerberg said, "Maybe."
"A lot of people who I think build startups or companies think that selling the company or going public is this endpoint," he said. "It's like you win when you go public. And that's just not how I see it."
Not everyone sees Facebook's rise as a good thing. Some question the depth of its social interaction, and many have raised questions over its attitudes about privacy.
Facebook has continually urged its users to share more personal information, often prompting criticism from privacy groups and users.
But Mr. Zuckerberg, now a celebrity himself and one of the world's youngest billionaires, sees Facebook as a universal identity system that could challenge Google and even e-mail for the basis of Internet communication.