I think, as always, generic statements can't be made. And one example shouldn't necessary serve as a general example. The willingness of a user to use Facebook

I think, as always, generic statements can't be made. And one example shouldn't necessary serve as a general example. The willingness of a user to use Facebook as a login identity is influenced by: 1. the trustworthiness/brand recognition of the service 2. expected behavior of the service with the data In this case, it seems to me as if there is no value a user would get from signing up with facebook besides the convenience. Furthermore, being an e-commerce service, I would actually say offering Facebook login is counter-productive because it may be perceived as a commercial use of your data (I know its irrelevant, but you would be surprised how often I have heard this) Also one should note that the averaging 30% really isnt that bad. 50% would mean its completely random, meaning there wouldn't be a preference either way. I wouldn't say people hate being forced at all. For obvious reasons, this post is biased towards selling their service.