I think you are referring to a Netflix documentary called “The Social Dilemma”, where ex-Facebook and Ex-Google employees talk about the “monster” they created.
A quick synopsis, from memory: When you do an internet search, the results are not uniform; they are tailored to your preferences, based on what is known about you. These companies have algorithms that try to predict what you want to read in order to get as much of your attention as possible (because more attention = more advertising revenue). They deliberately design their websites so as to make the material more addictive. They even slowly change your behaviour and views over time. An unexpected by-product of that is that various crack-pot conspiracy theories thrive (perhaps because the truth is boring) and people’s political views become more and more divided. The reason people’s political views become divided is that the info pushed to any individual will inevitably support that person’s political views, and so pretty quickly those at either end of the political spectrum live in alternative realities, and think the other side must be stupid or evil (because why else would their views be so contrary to the “facts” as they see them). The documentary particularly concentrates on the harm this is doing to children and teenagers.
Another similar documentary on Netflix from about 8 months ago is “The Great Hack”. Very informative, but it could have got to the point sooner. The documentary concentrated on Cambridge Analytica. Essentially, Cambridge Analytica data mined Facebook for huge amounts of personal details of individuals. It did this partly using surveys. It didn’t matter if a “user” didn’t respond to the survey, because the algorithms gathered data on all the “friends” of the “user”. Ie, if you had a Facebook “friend” who completed a survey, Cambridge Analytica knew a lot about you as well.
Cambridge Analytica then used the data to influence the outcome of elections. They had a spectacular success in a Caribbean country, and claimed success in a number of other countries. According to the documentary, the Trump team used Cambridge Analytica in 2016. Tactics were different for different countries, but for USA, they looked for what they termed, “persuadables”. These were a minority of the population why had the right level of fear etc that they though they could manipulate them by bombarding them with certain tailor-made stories and info. CA had so much data, that they knew which electorate each “persuadable” lived in. Hence obviously they concentrated on “persuadables” in swing states.
