Just to add to the brainstorm: they could charge users who have over, say, 5k followers a monthly fee to reach 100% of the audience instead of some arbitrary mi

Just to add to the brainstorm: they could charge users who have over, say, 5k followers a monthly fee to reach 100% of the audience instead of some arbitrary mix of them. The fee would increase with the # of followers. It's in the spirit of, but not exactly like, Facebook charging businesses to reach more of their followers by "boosting" posts. It would align the fees with the users who value most directly from using the service as a mass media broadcast device -- a lot of whom are businesses or quasi-businesses. They could waive fees for governments, educational institutions, non-profits, whatever.