Mortgaging your site to a closed-standards vendor gives them, not you, the economic power.
Another Matt from Alley ruminates on Medium’s uncertain future for publishers. I agree that these first couple of publishers probably got a good deal: better than free, they’re guaranteed money regardless of whether Medium makes money or not.
In making the decision to hitch their horse to Medium’s wagon while fording a river, they’re probably betting on Medium not going out of business, which I agree there’s only like a 10% chance of happening. However I think there is a 97% chance that Medium’s business model will change in the future because the path they’re on and these publishers are dependent on will not sustain their current costs or the investment they’ve raised.