Angst over Facebook's growing media influence is hitting new heights because of an allegation the social network is actively suppressing conservative news and opinions from its influential Trending Topics section.
The controversy has sparked debate about whether it's time for the new media powerhouse to be more transparent about how it works, or whether it has simply been hit with the same attack traditional media have had to defend themselves against for decades.
The accusation came last week in a report from technology news website Gizmodo, which quoted an unnamed former employee of Facebook. The individual had worked on the team that curates the trending section, which is most prominent on Facebook's desktop version.
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"Depending on who was on shift, things would be blacklisted or trending," said the source, a former journalist who self-identifies as conservative-leaning.
"I'd come on shift and I'd discover that CPAC or Mitt Romney or Glenn Beck or popular conservative topics wouldn't be trending because either the curator didn't recognize the news topic or it was like they had a bias against Ted Cruz."
Facebook quickly denied the allegation and shared some detail about how its trending topics are chosen.
Chief executive Mark Zuckerberg stressed the company's commitment to neutrality in what users see.
"We have found no evidence that this report is true," he wrote in a post on May 12. "If we find anything against our principles, you have my commitment that we will take additional steps to address it."
To that end, Zuckerberg met with prominent conservatives on Wednesday, including Beck, Fox News pundit Dana Perino and Donald Trump aide Barry Bennett. In a followup post, he said conservative news outlets and personalities such as Fox and Trump are popular and integral parts of Facebook, and that he has no intention of alienating their followers.
"I wanted to hear their concerns personally and have an open conversation about how we can build trust," he wrote.
News industry observers say it's an important issue given the social network's massive influence — 1.6 billion users and counting.
The site is rapidly becoming the main source of news for its users. About 63 per cent of Americans reported getting news on Facebook in 2015, a big jump from 47 per cent two years earlier, according to a Pew Research Center survey.
Many news organizations depend on Facebook for much of their traffic, which in turn helps fuel their advertising revenue.
Facebook maintains that what users see in their news feeds is dictated by impartial algorithms. The company says thousands of inputs go into what gets displayed, so liking a friend's photo or commenting on a story gives the algorithms more information on what specific users might like to see more or less of.
But Facebook employees play a major role curating the Trending Topics section. Much like the front page of a newspaper, it's a key piece of Facebook's real estate because it highlights what news other users are talking about or looking at. News organizations also often use those topics to inform or direct their own coverage.
"It doesn't tell us what to think, but it tells us what to think about," says Sidneyeve Matrix, an associate professor of media and film at Queen's University.
"It's worrisome that some of the stories we need to watch and see and hear may not make it through the censors because they're so concerned with keeping it relevant. Relevant becomes a synonym for personalized."
Google is another internet giant that wields tremendous media influence and has been accused of bias. The company faces antitrust charges in Europe for allegedly favouring its own services in its search engine results.
Some observers believe the pressure is building on these big internet companies to become more transparent about how they do business. Both Facebook and Google are known to jealously guard their algorithms and internal processes and deny attempts by governments and regulators to learn more about them.
"We need to have a better glance inside the machine and how decisions are made," says Dwayne Winseck, a journalism and communications professor at Carleton University.
"Common carriers — whether it's been post, roads, railways or telecommunication networks — because they are the funnel through which so much correspondence, goods and knowledge have to flow, have an obligation to serve all without discrimination."
Other media experts caution against making too much of the allegation against Facebook, since it's similar to the bias accusations traditional media have long dealt with. Such charges can often come from people with agendas.
"In my experience, people who are on the left and the right are always upset at various media for not being explicit supporters of their points of view," says Jeffrey Dvorkin, director of the journalism program at the University of Toronto's Scarborough campus. "They want the media to be their advocates and supporters."
Dvorkin recalls a conversation he had years ago with an American conservative when he was the ombudsman for National Public Radio. "I asked him, 'How do you know we have a bias against you?' and he said, 'We know it's not true, we just say that to put you on the defensive.'"