There are two problems with Facebook&#x27;s federated login.<p>For one: Facebook doesn&#x27;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&#x27;t want to login for work-related sites or apps with my Facebook account and I&#x27;m sure most wouldn&#x27;t login to a porn site with their Facebook account either.<p>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.