More than half of Facebook users log on to the site on any given day. Using software developed by outside parties — call it the Facebook economy — they share television shows they are watching, songs they are playing and photos of what they are wearing or eating. Facebook says 250 million photos alone are posted on its site each day.
To make money, Facebook sells the promise of highly targeted advertisements based on the information its users share, including interests, hobbies, private thoughts and relationships. Though most of its revenue comes from ads, Facebook also takes a cut from the money that apps make through its site. For every dollar that "FarmVille" maker Zynga gets for the virtual cows and crops it sells, for example, Facebook gets 30 cents.
For all of Facebook's success, the company has had its share of troubles. It went through a series of privacy missteps over the years as it pushed users to disclose more and more information about themselves. Most recently, the company settled with the U.S. Federal Trade Commission over allegations that it exposed details about people's private lives without getting legally required consent. And the legal fights over Facebook's origins have been embarrassing and sometimes distracting, though Zuckerberg has consistently denied allegations that have depicted him as a ruthless weasel.
Zuckerberg has made it clear he isn't especially keen on leading a public company. He has said many times that he prefers to focus on developing Facebook's products and growing the site's user base, rather than trying to hit quarterly earnings targets in an effort to keep investors happy.
Lately, though, he has matured into the role, said Scott Kessler, a Standard & Poor's equity analyst who follows Internet stocks.
"Clearly he is a very smart and shrewd person," he said.
Zuckerberg has surrounded himself with other savvy executives, who are often more experienced. They include Chief Operating Officer Sheryl Sandberg, who helped build Google's advertising business before Facebook lured her in 2008. Facebook's finance chief is David Ebersman, a former executive at biotech firm Genentech.
Amid the buoyant optimism about Facebook's prospects as a public company, some analysts see troubling parallels to the dot-com boom of the late 1990s, which turned into a devastating bust in the early 2000s. The biggest fear is that some investors will become so enamored with Facebook's brand and brawn that the will try to buy the IPO share with little financial analysis or recognition of the risks.
"It's a one-day circus," said John Fitzgibbon, founder of IPOscoop.com.
The IPOs of Zynga and LinkedIn showed that success isn't guaranteed even for profitable companies with huge followings. Zynga's stock is currently trading just slightly above its IPO price. LinkedIn is considerably higher, but still far below the $122.70 record that it hit on its first trading day.
"It seems there's so much excitement, innovation around Internet startups in Silicon Valley and yet a lot of these companies ... have not performed well at all," Kessler said. "The concern is the sustainability of the growth and profitability. It's very, very difficult to prove those things out over a short period of time."