Stephen Marche's Atlantic cover story about whether Facebook makes people lonely includes this sentence: "It's a lonely business, wandering the labyrinths of our friends' and pseudo-friends' projected identities, trying to figure out what part of ourselves we ought to project, who will listen, and what they will hear."

Is it a bad sign that this rings true to me? I don't mean that spending five minutes on Facebook leaves me despondent and alienated. But with both Facebook and Twitter, there's something weird about the experience that keeps me from diving in wholeheartedly.

Obviously, lots of people don't have this problem. I've always assumed that's because they're more extroverted than I am. But this theory has run into resistance from someone who should know--Susan Cain, author of the bestselling book Quiet: The Power of Introverts in a World That Can't Stop Talking. Here Cain, a self-described introvert, argues that things like Facebook and Twitter are in some ways friendlier territory for introverts than the actual physical world:

But if Cain doesn't think Facebook and Twitter are anti-introvert, she does think college admissions policies work against introverts, and she thinks this is bad for the world: