8. Mark Zuckerberg

Benjamin Wachenje

Chairman and CEO, Facebook
Born: May 14, 1984, White Plains, N.Y.
Education: Computer science, Harvard University (dropped out)

Mark Zuckerberg makes our anniversary list of the 25 most transformative leaders, icons and rebels of the past quarter-century by epitomizing both the social media revolution and the new generation of Silicon Valley entrepreneurs.

Facebook is the dominant social network in most of the world outside Russia, China and Iran. As of the end of last year, it claimed more than 1 billion users globally: 351 million in Asia, 276 million in Europe, 199 million in North America and 362 million elsewhere. It has annual revenue of $7.9 billion and a market valuation of $150 billion. No company ever become as valuable in its first 10 years. Bloomberg estimates that 10 of the top 23 Silicon Valley billionaires are Facebook co-founders, executives or investors.

The company last week earned a net profit per share of 34 cents a share before certain costs such as stock compensation–almost triple a year ago–on a 72 percent jump in revenues to $2.5 billion.

Zuckerberg was a billionaire by the time he was 23 and is about to turn 30 with a fortune Bloomberg estimates at $26.4 billion. That makes the Harvard dropout one of the 25 richest people in the world and the youngest of the top 150.

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The son of a dentist and a psychiatrist, Zuckerberg was raised in Westchester County, New York. He graduated from Phillips Exeter Academy in 2002 with a reputation as a programming prodigy. Turning down job offers from Microsoft and AOL, he headed for Harvard. There he created a Facebook forerunner called Facemash with friends, and then built the Facebook prototype, Thefacebook.

Zuckerberg has said that Facemash was developed to meet student requests for an online directory that the administration could not fulfill. But Harvard threatened to expel him for hacking into the school's computer network and copying private dormitory ID images. The charges were eventually dropped, but Zuckerberg, like many billionaire Silicon Valley entrepreneurs, remains disdainful of establishment institutions.

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Like Bill Gates three decades earlier, Zuckerberg dropped out of Harvard after two years to start his own company. Whereas Gates had moved to Albuquerque, N.M., Zuckerberg took his fledgling company to Palo Alto, Calif., securing $500,000 in funding from PayPal co-founder and venture capitalist Peter Thiel in return for a 10 percent stake.

Facebook's rapid growth has been astonishing even by tech start-up standards. It topped the 1 million-member mark in 2004, when it was still largely limited to university students and alumni. In 2006 it opened to everyone 13 and over, and passed 100 million users two years later. It hit 500 million users in 2010 and 1 billion in 2012.

The company's rising star drew lawsuits. One of them was filed by co-founder Eduardo Saverin, who paid for Zuckerberg's first servers but left Facebook in the summer of 2004. Tyler and Cameron Winklevoss, and Divya Narendra, sued Zuckerberg for allegedly stealing the idea behind Facebook. The suits (which were settled out of court) provided much of the story for the 2010 movie "The Social Network," whose portrayal of Zuckerberg is less than flattering. Like Steve Jobs, he is a ruthless destroyer of ill-formed arguments but equally blunt about shortcomings in his own products.

Zuckerberg took Facebook public in 2012, raising $16 billion in the biggest tech IPO ever—despite first-day trading glitches—and valuing the company at $104 billion. His challenge is continuing to grow and innovate. More than half of the world's Internet-connected population use Facebook, and the law of big numbers stares it down.

In response, Zuckerberg has been making Facebook an applications platform, with his $1 billion acquisition of photo-sharing app Instagram in 2012 an example of that strategy. Facebook is also going full bore for mobile. Last year, Zuckerberg formed Internet.org, an alliance of tech companies to deliver digital services over cheap phones to users in developing countries. He also must stay relevant to the new generation of digital natives so that Facebook, now 10, doesn't get a reputation of being the social network for old people.

Mark Zuckerberg: Lifelong highlights

• Captained Phillips Exeter Academy's fencing team
• Has New Jersey Gov. Chris Christie, U.S. Sen. Cory Booker, former French President Nicolas Sarkozy and U.S. President Barack Obama as likes on his Facebook page
• Has red-green color-blindness
• Rejected Yahoo's $1 billion offer to buy Facebook in 2005
• Signed Warren Buffett's pledge to give most of his money to charity

Read MoreFULL LIST: CNBC FIRST 25