Mark Zuckerberg, founder and chief executive of The Facebook social networking site that has more than half a billion users, was named Time magazine's 2010 Person of the Year on Wednesday.

Time defines the Person of the Year as the person who, for better or for worse, does the most to influence the events of the year.

"This year they passed 500 million users. ... The scale of Facebook is something that is transforming our lives. One in 10 people on the planet, and it's excluded in China where one in five people on the planet live," Time editor Richard Stengel said upon announcing the winner on NBC Television's "Today" show.

"It's not just a new technology. It's social engineering. It's changing the way we relate to each other. I actually think it's affecting human nature in a way that we have never even seen before."

Zuckerberg was a 19-year-old sophomore at Harvard University in 2004 when he started a Web service called Thefacebook.com from his dorm. Now he is one of the world's youngest billionaires and his privately held company is projected to have 2010 revenues of $2 billion, Time said.

Zuckerberg pledged a $100 million donation to the Newark, New Jersey, school system this year, and he was the subject of the Hollywood movie "The Social Network".

At 26 years old, Zuckerberg is the youngest winner since Charles Lindbergh was named the magazine's first person of the year in 1927 when he became the first pilot to fly solo across the Atlantic Ocean.

Since then the Time honor has become a cultural reference in the United States.

The award has had its controversy, such as when Adolf Hitler was named 1938.

U.S. Federal Reserve Chairman Ben Bernanke was the 2009 winner.

A Time poll showed readers favored naming WikiLeaks founder Julian Assange this year but Stengel said the magazine's editors and correspondents chose Zuckerberg after consulting among themselves, past winners and other world luminaries.

The conservative Tea Party political movement was Time's second choice for 2010 followed by Assange, Afghan President Hamid Karzai and the 33 trapped Chilean miners.