I was wondering what the best practice is when allowing users to sign up with multiple different services and email.<p>On our product, you can sign-up with email, Twitter, Facebook, Google and LinkedIn.<p>LinkedIn and Twitter do not provide an email so if you don't connect them to your original account, attempting to sign-in with them creates a new account.<p>With Google and Facebook, although they provide emails, it's often different than what the user connects to their original account.<p>Was looking for resources/best-practice feedback on this. Thanks!
This is a problem all sites with multiple sign on options face. I suggest going the Pinterest route of requiring the user to fill in email no matter which path they take.