My friend Jonathan Glick has a piece at Re/Code about the rise of what he calls "platishers."
A mashup of platform and publisher. Nice bit of word-work.
It's a nice but not a new idea. The 2014 version is closed, in the sense that content can not be shared between platforms. When I write something on Nick Denton's platform, I'm giving it to him. Same when I put it on Evan Williams's platform. It's only a good deal if you get something in return.
Some people will get more flow, as Twitter bumped the follower-counts for people they wanted to incentivize (maybe they did the opposite for people they don't like). Ultimately platforms that are closed-off serve as training wheels for the open systems that follow, in the normal cycle of technology.
Also, Scripting News was a platisher that formed the early blogosphere from its readership. We didn't hold them close, that wasn't the point. We wanted to change the topology of journalism, and learn from the transition.
Ultimately if Nick and Evan make it easier for people to get into publishing, they'll be providing a service. But to expect to hold on to them, that'll be what makes them want to go away. Imho of course.