The funny thing about all these frothy millions and billions piling up? Most of the value was created by people working free.

The Huffington Post, perhaps partly in an effort to polish the silver before going on the market, did hire a number of A-list journalists, but the site’s ecosystem of citizen bloggers and its community of commenters represent some share of its value. (How much is open to debate, as Nate Silver pointed out on the FiveThirtyEight blog.) Facebook, Twitter, Tumblr and Quora have been positioned as social networks, but each of them hosts timely content that can also be a backdrop for advertising, which makes them much more like a media company than, say, a phone utility…

For the media, this is a Tom Sawyer moment. “Does a boy get a chance to whitewash a fence every day?” he says to his friends, and sure enough, they are soon lined up for the privilege of doing his chores. That’s a bit like how social networks get built. (Just imagine if Tom had also schooled them in the networking opportunities of the user-generated endeavor: “You’re not just painting a fence. You’re building an audience around your personal brand.”)