Pretty interesting point. One thing that pops out to me is scale, not just of output from these systems but also input into them. For instance, newspaper, radi

Pretty interesting point. One thing that pops out to me is scale, not just of output from these systems but also input into them. For instance, newspaper, radio, and TV all reached unprecedented numbers of people, but they didn't bring the same scale to the number of folks contributing content. To use your Letter to the Editor example, a newspaper only has so much space, of which only a certain portion is allocated to displaying such letters. This means the vast majority of the country could never have their letter published just due to space limitations alone. Modern social media like Twitter is notably different because it has scaled the input just as much as the output. Every consumer can now be a producer as well. The idea that anyone can be a producer is very powerful and is what makes it feel more like a public space than, say, a newspaper.