EmailExists throws InvalidOperationException when EmailIsUnique is false

[danielwagn3r]

The methods EmailExists and GetByEmail of the UserAccountService throws a InvalidOperationException when EmailIsUnique is set to false in the MembershipReboot configuration.

For GetByEmail it might be resonable, as the method doesn't return a IEnumerable, but I don't get the reason for the behaviour of EMailExists.

For GetByEmail a API which returns IEnumerable to the multiple accounts would be great.