I think it's easy to blame the evil profit maximizing social media companies. But IMO even the most simple 'engagement' algorithm will produce negative externalities. Regardless of who's running it.

``` show_me_posts_people_like_me_have_liked()

- John saw 20 posts today and liked 9 of them.

- Cliff saw 20 posts today and liked 9 of them

- Jeff and Cliff had 6 overlapping likes

- Show Jeff the 2 extra posts Cliff liked; show Cliff the 2 extra posts Jeff liked

```

This seems like a simple / logical recommendation system. BUT the end result is that you make Jeff and Cliff closer to the same person over time. And times millions, you build echo chambers. And the biggest echo chambers (often those aligned with some identity politics) see they have a huge community and want to expand it. Making the whole platform worse as a byproduct.