[sulam]

Let me summarize it for you, since it's worth taking seriously:

1) Facebook has a view into the opinions and behaviors of the people that use it. Hopefully this statement is not controversial.

2) Facebook also has the ability to influence those opinions and behaviors, by controlling what you see when you use it. This statement may have been controversial at some point, but experiments have been run (by Facebook!) that demonstrate this is true.

Put the two together and you have a feedback loop that can be optimized to produce a particular set of opinions and behaviors. To pick an extreme (and extremely obvious) case, if Facebook decides it needs to goose revenue, one way to do that would be to selectively filter in the posts (both ads and non-ads) that reinforce purchasing things through Facebook ads.