I am the father of a teenager

Today, Valentine's Day, is my daughter Marina's birthday, and this year she turned 13. She had a party and a sleepover with some friends on the weekend, and today she set up a Facebook account—she herself wanted to wait until it was legitimate to do, unlike every other pre-teen in the world who simply lies about his or her birthdate to join early.

If you know her and you're on Facebook, she'll probably track you down and send a friend request. We've warned her to keep an eye out for spammy links and time-sucking apps. Some parents are still paranoid about letting their kids on Facebook at all, but I think most of those concerns (especially the ones about predatory adults lurking about) are overblown. Children need to learn how to be smart there, just as they do in other contexts.

Marina already has a smartphone, a Twitter account, a blog, and email—and the main thing we've had to help her with is the complexity of relationships with friends online, and how easily misunderstandings can escalate. That's an issue teenagers and their parents have to face offline too, and is nothing new.

I first went online around the same age, though "online" was rather different at the turn of the 1980s. I learned some hard social lessons, but I gained far more. I wouldn't be who I am today without nearly 30 years of electronic interactions.

It is astonishing that my wife Air and are the parents of a teenaged girl, however. No amount of time online really readies you for that.

Happy birthday, Marina. Welcome to the 500-million-strong club.