A lot of web applications allow users to login with facebook, I think the most important benefit from a user point of view is that he/she does not need to remember another set of username/email and password for a particular site.
However, from my experience, I find that many of these websites still ask for a username/email and password to create an account on their site after I have logged in with facebook.
Creating an account this way simply allows them to link my facebook account with the account on their website so that they can take advantage of using my facebook account to advertise themselves (e.g. post messages to the wall on behalf of me).
Which one is more common according to your experience?
- Login with facebook > Ask for username/email and password to create an account > Done
- Login with facebook > Done
Does this hurt user experience so much for the first scenario? Or it has already become a common practice that most users do not consider this as something bad?