The other night I was awake from 2:30am for no reason and I listened to this interview on the BBC app. Roger McNamee was an investor in Facebook and an influence on Mark Zuckerberg until a few years ago, when he realized what a detrimental effect FB and its algorithms have had on elections and discourse.
One of the things he pointed out was how, because of the specificity of ad/audience targeting, depending on how you have been pigeonholed, you will see completely different ads and news to someone else in a different pigeonhole. The world you see will be completely different to the one your more conservative or more liberal neighbour down the street. It's not like when we all shared the same experience and information when JFK was assassinated, or when the twin towers fell, or whatever iconic event you want to reference. People get completely different worldviews which don't overlap but only intersect in points of conflict.
Now me, I don't do facebook or twitter or any of that, but still, I read the Guardian and the NY Times and the Washington Post, and listen to NPR. My Trumpist sister-in-law gets her news from Faux News, conservative radio, Breitbart and Facebook. It's not surprising that we don't see the same universe.
McNamee also pointed out that the Russian (and other) disinformation campaign and bots etc, aren't hacking the system, they are using the system as it was designed, and that the flaw is in the system and the size of the system.
The TED Interview - Roger McNamee - @BBCRadio4Extra http://www.bbc.co.uk/programmes/m000bwqg
(The interviewer I recognized as the basis for one of the characters on W1A...)