Dave Winer with an insightful post about Medium, and why its dangerous if left unchecked.
We can avoid this, it's not too late. You have a choice. Post your writing to places other than Medium. And when you see something that's interesting and not on Medium, give it some extra love. Push it to your friends. Like it on Facebook, RT it on Twitter. Give people more reasons to promote diversity on the web, not just in who we read, but who controls what we read.
I appreciate this perspective, but I think its even broader than that. Yes, Medium is dangerous if it becomes too dominant, but that's true of any silo. I don't have a problem with companies like Medium (or Facebook, Twitter, Tumblr, or any other silo) existing. I have a problem with a world in which those companies exist at the expense of data ownership, uniquness of expression, privacy, and freedom of speech.
Wouldn't it be great if for-profit companies put more effort into making it easy for customers to own their own data, rather than just making it easy for customers to give their own data to a third party?