The Forbes 400: The Richest People in America, 2011

Luisa Kroll and Kerry A. Dolan

Jeff Bezos

Mike Segar/Reuters

Rank: 13

Net Worth: $19.1 Billion

Age: 47

Source: Amazon

Residence: Medina, WA

The mastermind of the world's largest online retailer Jeff Bezos got his start selling books. Now, thanks to the Kindle, he sells more e-books than the paper variety. Even Apple diehards are talking about the launch of Amazon's (Nasdaq: AMZN - News) "iPad killer" tablet later this year. He continues to fund secretive aerospace company Blue Origin, which shot into the news in August when an unmanned spacecraft blew up during a test flight. But Amazon shares have defied gravity, jumping 55% year-to-year and adding $6.5 billion to his net worth.

Mark Zuckerberg

Tony Avelar/Bloomberg via Getty Images

Rank: 14

Net Worth: $17.5 Billion

Age: 27

Source: Facebook

Residence: Palo Alto, CA

These days everything Mark Zuckerberg does grabs headlines, whether he's dining with President Obama, donating $100 million to Newark schools or vowing to eat only meat he's killed himself. In August a sale of Facebook shares by Interpublic placed a $66.5 billion valuation on the social network, helping to make him the year's biggest dollar gainer. Despite the jump, he spent a relatively modest $7 million for a Palo Alto house, where he and his longtime girlfriend, Priscilla Chan, now live. The long-anticipated IPO is likely to hit sometime in 2012.

Sergey Brin

David Paul Morris/Bloomberg via Getty Images

Rank: 15

Net Worth: $16.7 Billion

Age: 38

Source: Google

Residence: Los Altos, CA

Google's (Nasdaq: GOOG - News) Sergey Brin saw his cofounder Larry Page take back the reins at the search giant this year, replacing Eric Schmidt as CEO. Now the two are overseeing an effort to recoup some market share from much-hyped rivals, including Facebook. In June, the engine launched its social media project, Google+. Its Groupon killer, Google Offers, is now live in a handful of big city markets. The firm's Google Chrome browser now commands 20% market share, according to StatCounter, showing Google's increasing dominance outside of search alone. According to Alexa, is the most visited website in the world. Brin focuses on raising margins and directing special projects at the Mountain View, Calif.-based company. He emigrated from Russia at age 6. The son and grandson of mathematicians on his father's side, his mother was a research scientist at NASA. He met co-founder Page in a computer science Ph.D. program at Stanford and dropped out in 1998 to start Google from a friend's garage. The two share a 767 jet. Brin is also an investor in Airship Ventures and private space travel company Space Adventures. He has become a benefactor for research into Parkinson's disease, after finding out he has a genetic mutation increasing the odds he'll get it. (His wife Anne Wojcicki is the cofounder of personal genetics company 23andMe, through which he learned of his condition.) Brin practices diving, yoga and acrobatics to lower odds he'll develop the disease.

Larry Page

Reuters/Mario Anzuoni

Rank: 15

Net Worth: $16.7 Billion

Age: 38

Source: Google

Residence: Palo Alto, CA

Larry Page is back in the driver's seat at Google: he took over as CEO in April after ceding the role to Eric Schmidt a decade ago. Now the company must wait to see whether Page's return will boost Google's fortune in the long term. Since his appointment in April, stock price is down 10%. Page and co-founder Sergey Brin have already launched a host of new products this year, aimed at taking on Google's younger rivals. In June, the engine launched its social media project, Google+, a Facebook competitor. Its Groupon killer, Google Offers, is now live in a handful of big city markets. When he's not running the show, Page's personal passions include buying up chunks of residential Palo Alto for a network of houses that use new types of fuel cells, geothermal energy, and rainwater capture. He also rides a Zero X electric dirt bike and an electric sports car from Tesla Motors, in which he and Brin are investors.

John Paulson

Rick Maiman/Bloomberg via Getty Images

Rank: 17

Net Worth: $15.5 Billion

Age: 55

Source: Hedge funds

Residence: New York, NY

Call it the Paulson paradox. While his flagship fund has tanked 30% so far this year, as bets on Bank of America, Citigroup and China's Sino Forest went south, his personal fortune is up 25%, year over year. Reason? The gold-denominated versions of his firm's funds, where he is said to have most of his personal stash, have gained steadily. Last year his take-home pay was $4.9 billion, a record for the hedge fund industry. He is donating $15 million to a new maternity hospital in Guayaquil, Ecuador, where his father was born. Paulson became a billionaire in 2007 shorting subprime securities and earning a $3.5 billion payout. He got his start at Odyssey Partners, a private equity and hedge fund and later became managing director of M&A at Bear Stearns. He founded Paulson & Co in 1994.

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