Facebook wants its users to drive out fake news. Here’s the problem with that.

[Commentary] Mark Zuckerberg announced recently that Facebook plans to ask its community to help rate news producers’ credibility. Randomly selected users will be asked whether they are familiar with an outlet, and if so, invited to judge its trustworthiness. The ratio that results — of those who know the source, the proportion that trusts it — will “inform ranking in the News Feed” (though Facebook has remained vague about its relevance compared with other metrics). Rather than relying on expert judgment or hiring his staff to make those assessments, Zuckerberg has concluded that crowdsourcing is the “most objective” way to ensure “high quality” news on the platform.

But the reliability of this “trusted sources” measure is dubious, for two reasons. First, people in superficial surveys of this kind often indicate trust in fake sources that have familiar and vaguely credible names. Second, partisan Facebook users with a high interest in promoting “their” media could bias the results.

[Bernhard Clemm is a PhD researcher at the European University Institute, Florence.]