| There are 2 major problems that must be addressed: 1. Using OAuth to sign-up often means disclosing private data you can (and would normally prefer to) keep secret if you go the bare e-mail sign-up way. E.g. contacts list, exact date of birth, etc. - This is why I (as a user) stopped using OAuth for new accounts. Kind of the same used to apply to e.g. Android apps. I mean the "give an app all the permissions it wants or gtfo" anti-pattern which ought be abolished. The user should be allowed to continue after denying/revoking access to any (but absolutely essential for the very function) data silently or manually specifying whatever values they want. 2. It isn't always easy to decouple an OAuth-based account from the social network account, especially in case you loose access to the latter. - This is why I (as a user) migrated all OAuth-based accounts I had to the good old e-mail way. |
OAuth is an authorization protocol. It can be used (for example) to give Facebook access to your Flickr photos without having to give out your Flickr username and password to Facebook or share API tokens, and have a standardized way to revoke access when you realise Facebook scraped all your private photos.