I personally won't ever use Medium because it deprives the author of branding and recognition.
Why, simply because it's hosted on a different domain? It seems to help people reach an audience wider than they would otherwise, which is anything but bad for branding.
Besides, on the rare occasion I have read an article on Medium (I don't anymore) I could never remember the author. It's all just the faceless Borg.
For anyone thinking of using Medium, don't do it. It's like giving your work away for free, and for no recognition.