Our application has the following signup paths:
Twitter Connect Facebook Connect Email/Password
Once you signup with one, you have the option to connect either both social account (in the case of an Email signup) or the other social account (in the case of a Twitter or Facebook signup). By connecting each account you also have the ability to sign-in with that account going forward.
The question is, what's the best way to deal with potential orphaned accounts. For example:
User A signs up with Twitter account 'mytwitter'
User A signs out
User B signs up with Facebook
User B connects Twitter account 'mytwitter' to their Facebook login.
At this point User A's account would be orphaned.
I see a few options:
Always require an Email/Password no matter how you signup. This isn't ideal since it creates friction.
Merge User A with User B, which seems messy and has to have some privacy concerns.
Send a message to User B that that Twitter account already exists. That doesn't seem ideal either.
Anyone have experience with solving this? Seems like it would be a common problem.