Remember when Sarah Palin joined Al Jazeera America? Or Paul Krugman declared bankruptcy?

Neither of these stories were true. But in a social-media-driven news cycle that moves at perpetual warp speed, these falsehoods raced out ahead of the facts.

Now Facebook, clearly self-conscious about its role as a leading venue where these lies spread, is trying to enlist its own users as crusaders for accuracy. In a blog post on Tuesday, the company said it was adding an option to its social networking service that will let users flag news stories as hoaxes. If you elect to hide a post in your Facebook News Feed, the company explains, you will be able to flag it as "a false news story," in much the same way you can flag pornographic and violent content today.

The more times a post is flagged as false, the less often it will show up in News Feeds, the company says. Facebook won't delete heavily flagged posts, but they could end up with a disclaimer: "Many people on Facebook have reported that this story contains false information."

Nonetheless, this effort to crowd-source journalistic accuracy carries its dangers. Think The New York Times is a liberal rag spreading dangerous left-wing propaganda? Click. Think Fox News is run by a bunch of shills for the Koch brothers? Click. It's not like Facebook is asking for corroborating fact-checking before letting you click a button.

But Facebook claims the process works. "Stories that include scams, or deliberately misleading news, are reported two and a half times more often than links to other news stories," Facebook engineer Erich Owens and researcher Udi Weinsberg wrote.

The High Stakes of Hoaxes

Whether or not the crowd is as wise to journalistic fraud as Facebook hopes, the stakes for the company are high. As Facebook continues to grow in importance as a driver of traffic to online publishers' sites, clickbait mills have sprung up to feed on social media users' gullibility in the chase for ad dollars. Some of these sites' proprietors claim they're doing satire, but satire that doesn't really try to be funny is pretty much just lying. And the more these lies spread, the more Facebook's brand is tarnished.

Google faced a similar problem a few years back as content farms figured out how to game search, deluging users' top results with low-quality links. The search giant changed its algorithms, and content farms withered. Facebook faces a thornier problem, since its own users are in part culpable when fake news spreads.

One way to fight the virality of falsehood is to take Facebook's approach and turn the dial down on how often such stories show up for users. But in doing so, the company calls attention to the fact that the News Feed is not neutral. Facebook has not only an ability but an interest in exerting control over what you see and click. It's not a conspiracy. But it's another reminder that if you rely on social media alone for news, you might not be getting the whole story.