I'm not sure I buy the manipulation line either. People seek out information that fits their overall world view. It's hard to grapple with anything that challenges your beliefs. Insofar as people engage with bullshit on Facebook its probably because they already believe a particular thing, or it fits their existing beliefs. I highly doubt that facebook posts are changing a lot of minds. I'm also skeptical that it spurs very many people to actions they wouldn't otherwise take.

A lot of the news articles talking about the effects of facebook focus on how many people "saw" a particular post. Given how those impressions are gathered, I'm no convinced that a significant percentage of those impressions resulted in people actually reading the post or even the headline, let alone that resulting in any real world outcomes.

I think the people that build social media applications want everyone to think that they have the power to shape discourse and outcomes, and newspapers who's ad revenue is undermined by social media also want us to believe social media is dangerous. Those two things do not make it true.