That we are increasingly self sorting into politically isolated bubbles (based on where we choose to live / work) so we are less likely to encounter diverse opinions in real life [1]. Definitely agree that virality/discovery/engagement need to be carefully balanced, but I don't think that they are inherently good or bad. Virality/discovery/engagement can absolutely lead to the spread of misinformation, but it also is clearly a big driver for awareness of social causes like police brutality / BLM.

[1] https://www.amazon.com/Big-Sort-Clustering-Like-Minded-Ameri...

Could it be the big sort?

"Armed with startling new demographic data, [Bill Bishop] made national news in a series of articles showing how Americans have been sorting themselves into alarmingly homogeneous communities -- not by region or by state, but by city and even neighborhood. Over the past three decades, we have been choosing the neighborhood (and church and news show) compatible with our lifestyle and beliefs."

http://www.amazon.com/The-Big-Sort-Clustering-Like-Minded/dp...