Mark Zuckerberg of Facebook

If there is one thing you should know about Mark Zuckerberg, it's that you shouldn't second-guess him. It hasn't always been easy to heed that advice during his company's astronomical rise. He had an opportunity to become fabulously wealthy at the age of 22, when Yahoo offered to buy Facebook—which he still owns roughly 30 percent of—for $1 billion. He turned it down. Three years later, the Harvard dropout's company is worth 5 to 10 times more. He has radically changed the design of his social network—first to include users outside of academic institutions, then to de-emphasize activities he deemed less interesting than others, and ultimately to look a lot more like another hot social site, Twitter. Millions of users protested every step, using the very tools he created to threaten a mass exodus. He has stayed the course, and his site now boasts more than 300 million members, who spend more time on Facebook than any other destination on the Web. Like tech titans before him, Mark Zuckerberg is guided by the fundamental belief that he is right. And that conviction has alienated many of those around him—virtually the entire core team that surrounded Zuckerberg at Facebook's founding has since parted ways. But now, the kid whose business card once famously read "I'm CEO, Bitch" sits atop the most significant Internet company to emerge since Google. And that's in no small part a result of ignoring those who second-guessed him.

--
- Best, Tan Yinglan