Recently I wrote a post for the Hedgehog Review on the Substackification of journalism and whether it marks a permanent atomization of journalistic writing or whether it could be the seed of institutional renewal. Here are a couple of relevant data points: 

• On his Substack newsletter, Scott Alexander has been running book reviews by his readers. 
• On her Substack newsletter, Bari Weiss has been publishing essays by other writers, and explains that practice thus: "My goal is not to make a living publishing only my views —  or ones that conform exactly to my worldview —  on this Substack. (Trust me, it’d get boring.) My ultimate goal is far more ambitious. I want to run the most interesting opinion page in America, filled with fresh reporting and commentary.” 

Substack began as a way of highlighting distinctive individual voices; it’s already turning into something more collaborative.