We are currently using SharePoint 2010 and are potentially looking at SharePoint 2013 for an upcoming project.
The article below suggests that user profiles cannot be created from sources other than AD:
An important detail you must understand is that only AD or LDAP can be set up as a primary (or master) connection. A BDC connection cannot be. A primary connection means that a SharePoint profile with an account name (e.g. domain\username) can be created from this source. BDC can only be a secondary connection, meaning that it is only able to fill in additional properties for an existing profile—in other words, it cannot create a profile.
If true, this presents an issue for us as some of our other data sources have users that don’t exist in Active Directory, so we’d want to create profiles from them.
One suggestion we've had is to implement a service application that could then integrate with the user profile service, however I'm not quite sure how this would work.
Is a service application a good fit for something like this and if so, how would it look?
If not, is there any other solution?