Without that 4% Facebook runs the risk that users migrate to another social media platform, which could have a huge impact.

Milk might only account for 4% of a supermarket's sales, but a supermarket that doesn't sell milk is at a huge disadvantage to one that does.

From looking at my feed now I'd suggest its far more than 4%. All of the manufactured outrage and angry posting on news stories has disappeared leaving my feed with a few group posts and a bunch of ads.