After writing about four of these, though, I had a small epiphany; this is a ludicrously uphill battle, because Facebook and Google don't just make it easy to use their login because they're nice; the information that they gather from these logins is worth good money to them, and so of course facebook+google login is the most frictionless and butter-easy way to implement login.
Sigh.
Okay, I know this was totally obvious to everyone but me, but it does make me sad, and I can start to see the outlines of an internet that I'm somewhat less excited about than the one we have now.
I'll miss you, persona. Mozilla, keep up the good fight!