M'eh. I don't think there is actually anything to be learned here unless you think you can put up better up time numbers than Facebook. And if you can then it would be logical to go with only home grown authentication in lieu of all social providers, in which case you still end up in the "one basket" scenario.
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.
