one on oneHere’s a question: If something is shared online, but wasn’t broadcast to Twitter or Facebook, was it ever really shared at all? (Ha! And you thought the pond that inspired “Walden” was deep.) The answer, of course, is “yes,” and direct communication is becoming increasingly popular on the social Web.

Take Pocket, the read-it-later service formerly called, well, Read it Later: The service recently introduced a new “Send to Friend” feature that allows Pocket users to send articles directly to other Pocket-ers, bypassing Twitter and Facebook entirely.

“When you think about sharing and social and stuff like that you always think about Twitter and Facebook, but the reality is that most people are sharing in places that people never see it,” says Pocket CEO and founder Nate Weiner, adding that Pocket users share articles via email two to three times more than they share to Twitter and Facebook combined. (Whether or not Pocket users represent “most people,” as Weiner mentions, is up for debate.)

Or consider Rdio, which added user-to-user sharing to its service on Wednesday. Instead of sharing songs and albums via the large social networks — though they can still do that — Rdio users can now stay within the service.

And then there’s Snapchat, the ephemeral messaging app whose users now send more than 150 million photos each day. Each and every one of those photos needs to be taken in-app, preventing users from sharing to other networks. Hell, the photos self-destruct after just a few seconds; many users wouldn’t be able to get a photo out of Snapchat if they wanted to.

“[An image taken with Snapchat] might be a little grainy, and you may not look your best, but that’s the point. It’s about the moment, a connection between friends, and not just a pretty picture,” Snapchat says on its site. “The allure of fleeting messages reminds us about the beauty of friendship – we don’t need a reason to stay in touch.”

Even Facebook has started in on one-to-one communication — what it calls “private sharing” — with its newfound focus on messaging through Facebook Messenger or Facebook Home, which literally puts messaging and direct communication above everything else on a user’s smartphone.

All of these are the latest examples of what the Atlantic’s Alexis Madrigal calls “dark social,” or social tools — think Gmail, Google Chat, and other messaging services — that are essentially invisible to the rest of the Web. Many of these tools predate Facebook and Twitter, and show how the social equivalent to broadcast networks represent a much smaller chunk of “sharing” on the Web than previously thought.

[Image courtesy Scott Beale]