Excerpt from this article:
The social media company is increasingly becoming to the news business what Amazon is to book publishing — a behemoth that provides access to hundreds of millions of consumers and wields enormous power. About 30 percent of adults in the United States get their news on Facebook, according to a study from the Pew Research Center. The fortunes of a news site, in short, can rise or fall depending on how it performs in Facebook’s News Feed.
Though other services, like Twitter and Google News, can also exert a large influence, Facebook is at the forefront of a fundamental change in how people consume journalism. Most readers now come to it not through the print editions of newspapers and magazines or their home pages online, but through social media and search engines driven by an algorithm, a mathematical formula that predicts what users might want to read.