Greg, don’t worry.
Our mission is about enabling great ideas and stories have maximum impact. Therefore, we have not even contemplated a “strict” paywall. There is no scenario where readers would have to log in to read your work if you don’t want that.
FWIW, there is already paywalled content on Medium. Several publishers use our membership features and find, if they’re able to build a loyal audience, it’s a great alternative/supplement to sponsorships and ads.