The ConnectionFactoryRegistry won't allow multiple connection factories for the sample API type or for the same provider ID. So, if you try to register more than one FacebookConnectionFactory, an IllegalArgumentException will be thrown for the 2nd one indicating that there's already a connection factory for that provider ID. One option you have is to create a custom implementation of ConnectionFactoryLocator to allow for multiple connection factories of the same type. The registration of those connection factories should be easy to do, but you'll need to figure out how you want to implement the getConnectionFactory() methods to deal with the fact that there might be multiple matches.
All that said, I wonder why you would want to do this anyway. You have a single application, right? Why have multiple Facebook applications? I'm struggling to see a case where that would be needed. And even then, wouldn't it create a confusing situation with your users? Help me understand the use-case that would require a single application to connect to Facebook as if it were multiple applications.
Spring Social Project Lead