Andy,
You are right though we can block the user registrations through Hybridauth but registrations from "Create new account" are still possible. Right now the module allows creation of user accounts from the login page as well as the signup page. I wanted admins to control/decide whether new users creation is allowed or denied from the login page.
I want to make sure if user doesn't have a account in our application the only possible way to create account is from the signup/registration page but not form login page (treating them as they are already users of the application and creating user data for them.)
Steps to reproduce :
1) Configure Facebook widget(as example) and make the widget available on Login and Registration forms.
2) Open "user/login" page click on Facebook icon and enter the valid Facebook credentials.
3) It creates a account and redirects to the user profile page.
I want to control the step 2 by checking if the user email address is already assigned to any user in the application, if not don't create a account straight away show a validation message that you have to register into the application first.
I hope you are clear. Let me know if you still have concerns/suggestions.
Thanks,
Karthik