Medium is launching a paywall paid accounts, asking you to be a founding member. This means some of the content on the free publishing platform will be hidden from non-premium users. From the announcement:

You’ll have access to exclusive stories from leading experts, including your favorite Medium writers, on topics that matter not just today, but tomorrow too.

As always, own your content online, if you can. By all means, publish to Medium if you like (I’m playing with that), but make sure your online home is your own.