When the New York Times, the Guardian, HuffPo and the Atlantic all say X and a thousand blogs say Y, X is the story. We had alternative weeklies, zines and tape culture before the Internet, but the power to shape what people believed still belonged to a handful of organizations. The details have changed and which few organizations have that power has changed, but there's been no revolutionary change.
Right, and especially with the veneer of serendipity that you get from stumbling across (or upon ) a news article, it's easy to miss that there's a common set of beliefs behind most of it. They're not all that nefarious as hidden beliefs go, but you could still easily get the impression if all you read was these sites that you were doing everything a good democratic citizen should just by reading 8th grade reading level coverage that's designed not to scare off any advertisers. There's a huge unrealized potential for a more educated populace if we could collectively move past that.