For everyone waiting for Philadelphia's Google or Facebook, let me introduce you

The New Hope social networking site just raised $13 million from three venture firms. And while it's not the goliath those other Web businesses are, it's grown a lot in little more than three years.

I've Facebooked. I'm LinkedIn. Looking at myYearbook, I know I'm not the target demographic. Teenagers are.

And that has a lot to do with the teens who started the site back in April 2005.

Dave and Catherine Cook started with a simple idea: Turn the static high-school yearbook into a dynamic online experience.

After hiring programmers to build a Web site, the brother-and-sister entrepreneurs got their fellow students at Montgomery High School in Skillman, N.J., to create their own online yearbook pages.

Like so much of what happens online, the site went global in about six months. Dave and Catherine even convinced their older brother, Geoff, to become CEO.

In early 2007, myYearbook raised $4.1 million from U.S. Venture Partners, of Menlo Park, Calif., and First Round Capital, of West Conshohocken. At the time, it had more than 1.8 million members.

Today, it has more than 10 million members. Hitwise, which measures online traffic, says myYearbook is the third-largest social network in the U.S. - well behind MySpace and Facebook. But it recorded the fastest-growing market share between June 2008 and June 2007.

This latest financing was led by Norwest Venture Partners, another Silicon Valley fund willing to send its money East.

You don't shower $13 million on an enterprise unless you believe it's going to return in buckets. And it looks like myYearbook has figured out how to make money from teens being teens. That's what Norwest principal Sergio Monsalve noted: "What myYearbook has accomplished within the realm of online advertising is truly innovative."

Not too many businesses started by high-school students wind up raising $18.6 million. I hope they enjoy the ride.