There are two problems with Facebook's federated login. For one: Facebook doesn't need to know everything. While some are more peculiar about privacy than othe

There are two problems with Facebook's federated login. For one: Facebook doesn't need to know everything. While some are more peculiar about privacy than others, when information is used across boundaries that exist in our physical world, users start to care. I don't want to login for work-related sites or apps with my Facebook account and I'm sure most wouldn't login to a porn site with their Facebook account either. Second problem is that the whole idea of federated login is that there are many providers who implement the same protocol, meaning whatever account I have, I can authenticate myself. Only implementing Facebook defeats the purpose of federated.