21ST CENTURY RELATIONSHIPS: For Teens, Romances Where the Couple Never Meets Are Now Normal: A generation that lives online is redefining dating; ‘We only met for 20 minutes and that was the first and last time we ever saw each other.’

If we’re looking for an explanation of why today’s teens are having less sex than previous generations, there’s this: Many of them spend months or even years dating without ever meeting face to face.

When Nicole Nguyen was 16, she met her first serious boyfriend for the first and last time—after they’d broken up. They had 20 minutes. They hugged once. It only happened because that day, they just happened to find themselves in the same state.

Yet for an entire year, they spent almost every waking moment texting each other, talking on voice-chat apps, and even communicating over webcams through Skype and Oovoo. Ms. Nguyen, 24, is now a pre-kindergarten teaching assistant living in Brooklyn Park, Minn. To this day her parents have no idea they ever dated in the first place.

They might sound unusual: online relationships that bloom, reach a fever pitch of teenage intensity and—possibly—even wither before the two parties ever meet. But they’re becoming more common than ever. Ask any teenager—if they haven’t been in a relationship like this themselves, they can probably name friends who have.

I’m going to go out on a limb and say that this isn’t great.