SAN FRANCISCO -- Google co-founder Larry Page is known for his vision, passion and intelligence.
Yet there is a fair amount of concern that Page's other known traits -- his aloofness, rebellious streak and affinity for pursuing wacky ideas -- might lead the company astray. Page takes over as CEO on Monday as fast- rising rivals and tougher regulators threaten Google's growth.
Investors used to Google's consistency in exceeding financial targets worry that new leadership will bring more emphasis on long-term projects that take years to pay off. And many people still aren't sure that Page has enough management skills to steer the Internet's most powerful company.
Page already has learned that smarts alone won't make him a great leader. Although Page impressed Google's early investors with his ingenuity, they still insisted that he step down in 2001 as Google's first CEO.
He turned over the job to Eric Schmidt, a veteran executive who began working in Silicon Valley in the early 1980s while Page was still in grammar school.
Page's admirers say that at 38, he is more mature and less apt to be chronically late to meetings or tune out of conversations that don't stimulate his intellect, habits that he fell into during his first stint as CEO.
"There are parts of being CEO that don't fit Larry's personality," said Craig Silverstein, the first employee that Page and Google's other founder, Sergey Brin, hired when they started the company in 1998.
True to his taciturn form, Page hasn't said much publicly since Google made its stunning announcement in January that he will replace Schmidt as CEO. Google said Page wasn't available for an interview.
Still, Page has left little doubt about his top priority, which is to dissolve the bureaucracy and complacency that accompanied the company's transformation into a 21st-century empire.
Google is expected to end the year with more than 30,000 employees and $35 billion in annual revenue.
In Page's mind, the company needs to return to thinking and acting like a feisty startup. Rising Internet stars such as Facebook, Twitter and Groupon, all less than 8 years old, are developing products that could challenge Google and make its dominance of Internet search less lucrative.
Page has drawn comparisons to two high-tech geniuses who are even more accomplished, Microsoft co-founder Bill Gates and Apple co-founder Steve Jobs. Like those two pioneers in personal technology, Page invented and cultivated a product that changed the world.
But Page has yet to match them in the respect that as CEOs, Gates and Jobs brought out the best in the companies they created, delighting stockholders.
Page doesn't fit the CEO mold, even by the standards of Silicon Valley's free- wheeling culture. He dropped out of graduate school at Stanford to start Google and doesn't have a business degree.
Science and technology, though, seem to be in his DNA. His late father, Carl, was a computer scientist and pioneer in artificial intelligence, and his mother taught computer programming.
Page began working on personal computers when he was 6 years old in 1979, when home computers were a rarity. The geeky impulses carried into his adulthood, leading him to once build an inkjet printer out of Legos.
Page relishes challenging the status quo and encourages his employees to do so too. Those who know Page suspect that he picked up the anti-establishment mindset as a boy who attended Montessori schools, which encourage independent activities.
Page has wanted to control his own destiny, and legacy, since reading a biography of the inventor Nikola Tesla before he was in high school. Tesla wasn't rewarded or widely recognized for his breakthroughs in X-ray, wireless communications and electricity. Page didn't want that to happen to him as an entrepreneur.
For that reason, Page embraced the chance to be Google's CEO when the company started in a rented garage not far from the company's current headquarters in Mountain View, Calif.
It also helps explain why he and Brin created a separate class of stock with greater voting power so they and Schmidt could remain in charge after the company went public in 2004. Page's stake in Google has made him one of the world's wealthiest people with an estimated fortune of $20 billion.
Although the contours of his personality and background are known quantities, Page remains an enigmatic figure on Wall Street.
He remains well known for uncompromising idealism, reflected in his embrace of his company's "Don't Be Evil" motto and his pledge to never cater to investors' desire for ever-rising quarterly earnings at the expense of long-term investments.
Page already raised concerns by pushing Google into renewable energy and robotic cars. Those who know him said he has discussed even more far-flung projects behind closed doors.
"Sometimes his ideas are just way out there and you're kind of like, 'Wow, that came out of left field,' " said Ethan Anderson, a former Google product manager who now runs Redbeacon, a startup that operates a search engine for finding neighborhood businesses.
Uncertainty about whether Page will be as interested as Schmidt in appeasing Wall Street has contributed to a 6 percent drop in Google's stock price since the CEO change was announced Jan. 20. The technology-driven Nasdaq index has added 3 percent during that time.
BGC financial analyst Colin Gillis doesn't believe it's a coincidence that Google revealed that it would hire more than 6,200 employees this year less than a week after it announced Page's comeback as CEO.
"Don't be surprised if Google's spending goes up, even if it means its earnings per share might go down," Gillis said.
Page's supporters believe Google's current market value of about $190 billion will climb even higher under his leadership. That would mirror what happened after Jobs finally got his chance to run Apple in 1997 after a decade in exile.
Since then, Apple has brought out the iconic iPod, iPhone and iPad devices and created more than $300 billion in shareholder wealth.