Try to guess America’s most engaging social network. Facebook? Wrong. Twitter? Wrong. Pinterest? Wrong again. According to comScore‘s most recent social networking data, from the month of March, the San Francisco based site Tagged engages users like no other service. It was the only site to finish in the top two in both of comScore’s engagement metrics.

Tagged users visited an average of 18 times each during March according to ComScore, second only to Facebook’s average of 36 visits per vistor. And each time a Tagged user visited the site, he or she stuck around for 12.1 minutes — which trailed only Tumblr (14.7 minutes) and beat out Facebook (10.9 minutes).

Tagged co-founder and CEO Greg Tseng says he’s happy about ComScore’s March data, but that his company has been among America’s most engaging social networks for about a year now. The secret to Tagged’s success? A pivot Tseng and co-founder Johann Schleier-Smith made around the beginning of 2008.

The longtime friends started Tagged in 2004, at the time angling it to be a Facebook-like social network for high schoolers. Eventually, however, Facebook expanded beyond a closed college network and allowed anyone over the age of 12 to join.

“We took a hard look and decided we weren’t going to win,” Tseng says. “But we had found out a lot of our users were actually using Tagged to meet new people, so that led us to pivot into a new space called ‘social discovery,’ where people use sites to make new social relationships.”

As opposed to sites like Facebook, where people primarily organize and maintain relationships established offline, Tagged functions mostly as a portal to meet new people online for romance or simply friendship. The site’s algorithms encourage users to connect based on shared interests, tastes and hobbies.

Tseng says Tagged’s 10 million core monthly active users form an average of 100 million new connections per month. The site has been profitable since 2008, and over the past year tripled its staff to a current count of more than 170.

With social discovery as a whole seen by many to be a rising tide, Tseng believes Tagged’s success will continue to grow.

“If I look out at the next five or 10 years, I really see social discovery as big as social networking — in some sense I think you can think of social discovery as the engine for social networking,” he says, referencing Dunbar’s number, which theorizes that humans can maintain an average of 150 connections at a time.

“Facebook is the place where you maintain your current 150,” he says. “And Tagged will be the place where you refresh that 150.”

Do you think social discovery is the next big thing? Let us know in the comments.

Image courtesy of iStockphoto, akinbostanci

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