The point is NOT that "famous" people have opinions. Of course they do, for the same reason that nobodies like us have opinions. The Wall Street Journal is absolutely welcome to tell you to vote for Trump if you happen to be reading its editorial page. Your union leadership is welcome to tell you they think Warren is great and endorse her; you voted for them and presumably you care about their opinions. Taylor Swift has been known to endorse the occasional candidate too. Shaping our opinions based on those of people we trust is the way things are supposed to work.

The problem with paid advertising is that this breaks down. Now it's not the "people" we trust that are telling us this stuff, it's the "places" we go to find those people. There's a difference between Zukerberg telling us who to vote for and Facebook taking money to plaster our feed with Bloomberg ads. So people who are likely to "trust" their Facebook feed (which is most people) are now at the mercy of whoever is willing to pay Facebook the most money.