>The author supposes that there are some mustache-twirling masterminds behind the scenes at Google, Twitter, and Facebook, picking and choosing what content is promoted. But the algorithms, at there most basic sense, promote what is popular.

Hardly. The algos have programmers thumbs on them heavily. A hilarious example was when Reddit was trying to deal with the_donald successfully spamming reddits hot algorithm. But someone screwed up the new weighting and instead of pushing td posts down it pushed them up, the whole front page was nothing but td posts for a day. They eventually fixed it, but never think that there isn't a human jury rigged mess of if else statements at the core of the algorithms.