SAN FRANCISCO – Mark Zuckerberg, Facebook's chief, has managed to amass more information about more people than anyone else in history.

Now what? As Facebook turns to Wall Street in the biggest public offering ever by an Internet company, it faces a new, unenviable test: how to keep growing and enriching its hungry new shareholders.

The answer lies in what Facebook will be able to do – and how quickly – with its crown jewel: its status as an online directory for a good chunk of the human race, with the names, photos, tastes and desires of nearly 1 billion people.

Already, lots of investors are scrambling to buy Facebook shares, with giddy hopes that it will become a big moneymaker like Google. In the eight years since it sprang out of a Harvard dorm room, Facebook has amassed users at breakneck speed, kept them glued to the site for longer stretches of time and turned a profit by using their personal information to customize the ads they see.

Whether it can spin that data into enough gold to justify a value of as much as $86 billion remains unclear.

"We know Facebook has an awful lot of data, but what they have not worked out yet is the most effective means of using that data for advertising," said Catherine Tucker, a professor of marketing at the Sloan School of Management at the Massachusetts Institute of Technology. "They are going to have to experiment a lot more."

Analysts, investors and company executives can rattle off any number of challenges facing the company. As it works to better match ads to people, it has to avoid violating its users' perceived sense of privacy or inviting regulatory scrutiny. It needs to find other ways to generate revenue, like allowing people to buy more goods and services with Facebook Credits, a kind of virtual currency. Most urgently, it has to make money on mobile devices, the window to Facebook for more and more people.

All the while, its ability to innovate with new features and approaches – to "break things," in Zuckerberg's words – may be markedly constrained once it has investors to answer to.

"They are going to have to think about whether they can continue with the motto 'Done is better than perfect,' " said Susan Etlinger, an industry analyst at the Altimeter Group. "When you're operating as a public company, life is very different. We haven't seen that play out yet. It's going to take a few quarters to figure out what a public Facebook is going to look like."

Skeptics point out that the company's revenue growth showed signs of slowing in the first quarter of 2012. And a Bloomberg survey of 1,253 investors, analysts and traders found that a substantial majority were dubious about the eye-popping valuation Facebook was seeking.

"It's a risky asset. No doubt about that," said Brian Wieser of Pivotal Research Group. Still, Wieser says he thinks that Facebook is worth $83 billion and that its revenue will grow by at least 30 percent for the next five years.

The most pressing issue for Facebook executives may be the mobile challenge. Already, more than half of Facebook's 901 million users access the site through mobile devices. In regulatory filings, the company says mobile use is growing fastest in some of Facebook's largest markets, including the United States, India and Brazil. Facebook goes on to acknowledge that it makes little to no money on mobile and that "our ability to do so successfully is unproven."

There is not much space on mobile screens to show advertisements. And Google and Apple, two of Facebook's biggest rivals, control the basic software on most smartphones, which could make it harder for the company to make inroads there.

Facebook's response has been to aggressively acquire companies focused on mobile, including Instagram, for which it paid $1 billion in April. But it warned in a revision to its offering documents last week that the mobile shift meant it was adding users faster than it was increasing the number of ads it displayed.

What Facebook has – more than any other digital company – is a spectacularly rich vault of information about its users. Average Americans now spend 20 percent of their online time on Facebook alone, thanks to the ever-growing menu of activities the company has introduced, from playing games to sampling music to posting pictures of baby showers.

How Facebook exploits its users' information – and how those users react – are the next challenges.

David Eastman, worldwide digital director for the advertising agency JWT, said Facebook would need to give marketers more data about what kinds of users click on what kinds of advertising, and about their travels on the Internet before and after they click on an ad.

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