Currently a user that logs in with a social network has one internal IDM user that represents the user. If the same user logs in with a different social network another IDM user is created for the user.
It should be possible for a user to associate multiple social network accounts with the same internal IDM user. The user should then be able to login with any of the linked in social networks to the same account.
It should also be possible to link existing accounts. For example a user that has logged in with Google and Facebook, but didn't choose to link the account on first login. In this case the multiple internal IDM user should probably be merged into a single IDM user.