Newsletter industry study, part 2

Here are the questions/topics I am thinking about exploring in reference to my earlier post about doing a newsletter industry study.

Comment and suggestions welcome!

1. What are the major trends shaping the industry?
2. Who are the major players?
3. What are the business models being used successfully?
4. Is the space too crowded already or are there still opportunities?
5. What options are there for the tech stack?
6. Overview of marketing strategies.