I'd add the active component of Facebook compared to tabloids/broadcasts. With the latter, I'm just a consumer. With the former, I'm actively contributing via share/like/comment. There's probably a psychological component that deepens your commitment to the viewpoint when you actively participate like that.

They also aren't personalized, which has more side effects than people realize.

Even the most nihilist shock-jock has to pick a speed that won't alienate half his audience or drive all the advertisers away from the network. In these systems, those counterweights don't exist.