I think it's not so much Facebook alone but the entire Internet. The connectivity between humans is suddenly increased manyfold, and reaches much wider. Imagi

I think it's not so much Facebook alone but the entire Internet. The connectivity between humans is suddenly increased manyfold, and reaches much wider. Imagine using a graph layout tool on a giant graph with only few localized connections. Likely the picture will have evenly distributed nodes without much movement. But then as you dump all these new edges onto the graph, the nodes start to move into rigid clusters separated by weak boundaries. I think this is what's happening with the red/blue, vax/antivax etc. groups.