SAN FRANCISCO -- Seventy-two hours before Facebook's big moment earlier this month, Sheryl K. Sandberg was half a world away, hobnobbing with Archbishop Desmond Tutu and others.

Yes, Sandberg is Mark Zuckerberg's No. 2. And, yes, if all goes well, she will soon become the $1.6 billion woman. On Feb. 1, Facebook filed to sell stock this spring in an initial public offering that, in all likelihood, will instantly make it one of the most valuable corporations on the planet.

But Sandberg, who has helped steer this social network to this once-unimaginable height, had more on her mind than securities filings and ad metrics. She was attending the annual World Economic Forum, in Davos, Switzerland, where her subject wasn't Facebook but women. Specifically, how women, in her view, must take responsibility for their careers and not blame men for holding them back.

Given that Sandberg is Facebook's chief operating officer,

and that all of Wall Street was hanging on the IPO news, you might think that she was absurdly off-topic. But Sandberg sees herself as more than an executive at one of the hottest companies around, more, too, than someone who soon will rank among the few self-made billionaires who are women. She sees herself as a role model for women in business and technology. In speeches, she often urges women to "keep your foot on the gas pedal."

Strategy

Her call isn't simply about mentoring and empowering. It is also about business strategy.

A majority of Facebook's 845 million users are women. And women are also its most engaged users. So Sandberg is playing to a powerful and lucrative demographic, as well as to advertisers.

Inside Facebook's headquarters in Menlo Park, Calif., she is considered a not-so-secret weapon for recruiting and retaining talented women as well as men. She and Zuckerberg will need the best brains they can find to sustain Facebook's astonishing growth.

Of course, it helps that Sandberg has personality and presentation skills. In Davos and on the conference circuit, in public appearances in Washington and on college campuses, she has a warm, disarming tone that sets her apart from many other executives, male or female.

Her talks have gone viral. On YouTube, videos of her speeches have been viewed more than 200,000 times. Some have been included on syllabuses at the Stanford and Harvard business schools. She exudes that certain something that seems to leave many people, particularly young women, a bit star-struck.

"There have been a handful of women that could have been the 'Justin Bieber of tech,' but Sheryl is the real deal," said Ann Miura-Ko, a lecturer at the School of Engineering at Stanford and an investment partner at Floodgate, a venture capital firm in Palo Alto, Calif. "Young women really want to be her and learn from her."

Miura-Ko added: "Sheryl is radioactive plutonium when it comes to a recruiting weapon within Facebook."

Other women in Silicon Valley have been role models. Many, like the Google executives Marissa Mayer and Susan Wojcicki, have quietly campaigned to promote women inside their companies. Others, including Meg Whitman, the former chief executive of eBay who now runs Hewlett-Packard; Carly Fiorina, the former HP chief; and Carol Bartz, the former head of Yahoo, have reached pinnacles of success in tech.

But none has made promoting women a cause the way Sandberg has. Even so, some say her aim-high message is a bit out of tune. Everyone agrees she is wickedly smart. But she also has been lucky and has had powerful mentors along the way.

After Harvard and Harvard Business School, she quickly rose from a post as an economist at the World Bank to become the chief of staff for Lawrence H. Summers, then-treasury secretary. After that, she jumped to Google and, in 2008, to Facebook.

She is married to Dave Goldberg, a successful entrepreneur and the CEO of SurveyMonkey, which enables people to create their own Web surveys. She doesn't exactly have to worry about money. Or child care. She and her husband have two young children.

To some, Sandberg seems to suggest that women should just work harder while failing to acknowledge that most people haven't had all the advantages that she's had.

''I'm a huge fan of her accomplishments and think she's a huge role model in some ways, but I think she's overly critical of women because she's almost implying that they don't have the juice, the chutzpah, to go for it," said Sylvia Ann Hewlett, president of the Center for Talent Innovation, a research organization on work-life policy, and director of the Gender and Policy Program at Columbia University.

''I think she's had a golden path herself and perhaps does not more readily understand that the real struggles are not having children or ambition," Hewlett continued.

"Women are, in fact, fierce in their ambition, but they find that they're actually derailed by other things, like they don't have a sponsor in their life that helps them go for it."

Making a mark

There's no denying that Sandberg has been remarkably successful at Facebook. When she joined the company, it had some 70 million users and no business model.

With her in the COO seat, profits have reached $1 billion on $3.7 billion in revenue.

She has arguably made an equally big mark with her frequent speeches to women, which are a call to draw more women to technology, and to Facebook. She personally recruited Lori Goler, its head of human resources, and Katie Mitic, its head of platform and mobile marketing.

Sandberg's role in keeping such employees has been even more crucial.

Sukhinder Singh Cassidy, who worked with her at Google, said Sandberg's high profile gave Facebook an edge in recruiting and retaining talent.

''When you have women who say, 'Can I stay in? Can I have children and make it still work?' the existence of role models like Sheryl is very impactful," said Singh Cassidy, who now runs a video shopping startup, Joyus.

In the money

If Silicon Valley men bond in venture capital conference rooms or on weekend bike trips, Sandberg has been building an alternate networking group of Silicon Valley women. For about seven years, since she was a Google executive, she has held catered monthly dinner parties at her home for a group of several dozen women.

For all her roles and titles, Sandberg is about to add one more: billionaire. According to Facebook's filing, Sandberg made nearly $31 million last year, including base salary, bonus and $30.5 million in stock awards. She owns 1.9 million shares in the company and an additional 39 million in restricted stock options.

If Facebook goes public at a valuation of $100 billion, which Wall Street sees as a possibility, her stake could be worth as much as $1.6 billion. She would rank among the richest self-made women in America.

Many wonder whether Sandberg might reach beyond Silicon Valley and into the world of politics. That was the buzz at Davos.