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Why do some stories abruptly disappear from Digg? Duncan Riley of TechCrunch suspects "super users." But there's a much simpler explanation: Digg's shadowy moderators. Digg cofounder Kevin Rose has admitted that the social-news site, a supposedly democratic venue where users pick the headlines, employs moderators: "We have site moderators that ban spammers, remove illegal content, and keep an eye on things. Always have, always will." But what, exactly, does keeping an eye on things entail?

According to someone who was approached about a job as a Digg moderator, Digg uses one moderator per topic, and their duties go far beyond patrolling the site for spam. While they don't have the power to launch a story straight to the homepage, they can adjust the criteria to make it easier or harder for a story to make it big. And in so doing, of course, they exercise editorial judgment. When you submit a story to Digg, it's not just in the hands of the users; it's also at the mercy of unnamed Digg editors.

What does this say about Digg? First, that it has failed to match its aspirations as a perfect democracy of news. And second, that as a business, it may be less attractive than some think. The craze among investors these days are for startups where users generate the content, for free, while paid workers do as little work as possible. At Digg, it turns out Tom Sawyer is painting the fence, after all.

What should Digg do? As Rose points out, Digg does need to do some policing of the site to deter spammers and criminals. And spelling out what moderators do could make their jobs harder, as people will inevitably use the information to try to game Digg.

But I think Digg needs to err on the side of transparency here. When a moderator gives a story an assist, or holds it back, users deserve to know what's happened, and why. Otherwise, conspiracy theories about "super users" will continue to circulate. Digg has in fact begun to change the news business, making traditional editors more accountable to their readers. It's time Digg's editors were, too.