It is a failure of imagination to think that our choice is the social media platforms we have now or nothing. I keep thinking about something that Robin Sloan, a novelist and former Twitter employee, wrote this year: “There are so many ways people might relate to one another online, so many ways exchange and conviviality might be organized. Look at these screens, this wash of pixels, the liquid potential! What a colossal bummer that Twitter eked out a local maximum, that its network effect still (!) consumes the fuel for other possibilities, other explorations.” What’s surprised me most as...