Using FBOauth, only allow existing users to associate a Facebook account How might I configure a login scheme where by 


if someone already has an account on the site they may associate a FB account and login with it
But yet, deny login to any FB account that is not already associated with an existing account


Is something like this approachable? 

In other words, I don't want random FB accounts to log into a Drupal instance but yet, want to allow existing users to associate a FB account with their Drupal login.
It turns out the FBOauth modules checks for the ability to create new accounts. Since we've limited our system only to User 1 and LDAP, no new FB accounts appear to be created. This leaves the user only to log in with an LDAP/AD account and then associate FB and their Drupal account. That is the exact behaviour for our use case!