I'm noticing very little discussion about the user aspect, and I say that with non-savvy users in mind. I run a mid-sized web app/community where I've been supporting such users for a long time.<p>Right now, I offer a classic login, and a few social providers. You'd think this is straightforward to support, but about 70% of support requests consists of the endless ways in which users can mess this up.<p>"Can't get in"<p>Try recover password. Email didn't come. Because they entered the wrong email. Correct email this time. No wait, think I signed up with a social account, not sure which one, have many. Login worked. Wait now it doesn't again (saved browser password did not update).<p>This is just the tip of the iceberg. This new solution, whatever merit it has, is going to be additive. It won't replace anything, it's yet another way to log in, if at all, as it depends on websites implementing it and about 90% of the web is basically not maintained.<p>So it's only adding complexity/confusion specifically to these users, which I consider to be the vast majority. In turn leading to more support headaches.