SAN JOSE, Calif. -- It's half an hour before the chief executive officer of Silicon Valley's hottest social network is set to take the stage, and it's already standing room only at the Startup Grind gathering in Palo Alto, Calif.
The bi-monthly gathering of tech entrepreneurs has nabbed some high-profile speakers in recent months. "The crowd was big for Kevin Rose," Dave Wamsley, a regular attendee, says of the Digg.com founder. "But now Elvis has entered the building."
Elvis, it turns out, is a baby-faced native of Iowa with a somewhat shy mien. Ben Silbermann is also CEO of one of the fastest-growing Web sites in history -- Pinterest, which lets its 12 million-and-counting users collect and share digital images and link them to Web sites.
Mr. Wamsley, a serial entrepreneur who's been in Silicon Valley since the dot-com era, said he hasn't seen a startup take off overnight like this since Netscape.
Indeed, Startup Grind founder Derek Anderson admitted while chatting onstage with Mr. Silbermann last week he'd never heard of Pinterest until a year ago, when he asked his wife, "What's that on your computer?" Turned out she'd spent every night on the site, looking for recipe tips and the like -- for four hours a pop. Before long, all her friends were too, in keeping with the site's heavily female demographic.
Mr. Silbermann's wife, for her part, was key to getting her husband to finally tackle the startup he'd been talking about for years while holding down a customer support job at Google. "She said, 'You should do it or shut up about it,' " Mr. Silbermann told the audience.
He sounds slightly thunderstruck by the site's wildfire growth: Pinterest is the 16th most-visited Web site in America -- ahead of CNN.com and ESPN.com -- and the 50th most popular in the world, according to ranking service Alexa.
Venture capitalists who, two years ago, didn't understand the startup now are clamoring to follow in the footsteps of Netscape co-founder Marc Andreessen, whose venture firm in September led a $27 million investment. Big-name media have come calling to interview Mr. Silbermann and been largely rebuffed.
"We've been too busy to hire a press person yet," he said, almost apologetically.
All Mr. Silbermann wanted, after all, was a place to help people share their hobbies.
The son of two family-practice physicians in Des Moines, Mr. Silbermann grew up collecting leaves and insects. He went to Yale figuring he'd follow in the family trade, then switched to political science. After graduating in 2003, he landed a consulting job in Washington and joined the firm's technology practice because, he said, that's what was open.
But even though he'd grown up a Luddite -- his father still refuses to ditch the family's old VCR -- Mr. Silbermann saw the changes being wrought by Web 2.0.
"I felt like the story of my time was happening in California," he told last week's crowd, "and I wanted to be part of it."
The Google job, he said, taught him a lot, but as a nonengineer in a company that prizes tech skills, his ceiling was limited. After his wife's tough-love pep talk, he finally took the plunge -- right before the 2008 Wall Street meltdown made it nearly impossible to raise money.
It didn't help that Mr. Silbermann's two co-founders were as nontechnical as he was.
But as he kept refining his idea during long hours at Hacker Dojo, a Mountain View, Calif., hothouse for techies, he became more convinced of the potential of a clean, colorful interface that would let users collect and "pin" digital images -- much the way he'd pinned and displayed insects as a boy.
"A 'pin' is a digital representation of an object that means something to you," he said. "When you open the site, you should see things that you love -- and be able to connect to the people who found them."
After the site launched in January, 2010, however, the going was slow. Four months in, Pinterest had 200 users; half were Mr. Silbermann's friends in Des Moines.
Then on a whim, he attended a conference of interior designers, who immediately grasped the appeal of a site where they could compile interesting design possibilities gleaned from around the Internet. Thanks to word of mouth and the courting of a handful of bloggers, Pinterest's traffic began growing at 40 to 50 percent each month -- and it hasn't stopped.
What makes that dizzying pace even more remarkable is that the site is still invitation-only; potential users have to seek approval to join, though that's largely a formality.
Asked how the company plans to make money from a fast-growing and fanatical following that exceeds the combined populations of New York and Los Angeles, Mr. Silbermann said he "hasn't really focused on it."
But even though Pinterest has just 20 employees, it already has spawned its own cottage industry. Among the Startup Grind crowd of more than 200 was Matt Monday, who recently moved to Silicon Valley from Toledo and launched a start-up to help nonprofits reach supporters on Pinterest.
Big-name brands that market on the site include Gap, Whole Foods, and CBS, all eager to court Mr. Silbermann's sprawling user base.
And while Mr. Silbermann didn't set out to create a Web site that caters to women, the crowd was noticeably more female-laden than usual Startup Grinds, organizers said.
Among those on hand to catch a glimpse of Mr. Silbermann was Dee Marcyes, who's married to the co-founder of social networking startup Plancast. Her husband frequently makes the tech-mixers rounds but had never been able to coax her to join him.
But Ms. Marcyes -- who visits Mr. Silbermann's site every day for tips on cooking and parenting -- came along this time with an eager smile and the couple's toddler in tow.
"I'm here," she said simply, "because it's Pinterest."