Yeah, I really didn't want to bring up politics (since it's not one, not two, but who knows how many cans of worms) but politics are a really good example of how social media work and "soft censor" speech. Another good example would be academia and how it's borderline dangerous to express any non-liberal opinion there, or worse publish or just do research that's not colored with liberal ideology. People get expelled, suspended, etc..
But again, I'd rather not talk politics. Gib RTwP.