Facebook JavaScript authentication is down
developers.facebook.com
developers.facebook.com
People will choose a single authentication scheme when joining a web property or app so not "putting all your eggs in one basket" doesn't really apply. If Facebook authentication is down I'm not going to hope that the website owner implemented multiple authenticators so I can create a brand new account tied to my Twitter identity, I'm just going to leave and come the next day. To users, the only ones that really matter, they don't care about all eggs and all baskets, they care about their one egg and one basket combination.