I've got a facebook iframe application that uses standard facebook multi_friend_selector.php page to invite friends into the application. Both invite friends and invite via email options are enabled.
1) Invite by Id. When a user select one of his friends (by id) and sends a request, a facebook request with the link to the special page of the application is created. So user can enter the application using this link and the application can track who invited him. This case is OK.
2) Invite by email. When a user invites the friend by email and enters the email of the user that is not already in a facebook. The facebook sends a registration invitation on the entered email. After the user registers in facebook (using the link in the email), he has one friend - those person who invites him, link to the application, but he does NOT have any requests. So when the user enters the application, the application could not track who invited that user to the application (Of course if the functionality that asks the user who invited him is not implemented).
What would you recommend in this situation to track who invited the new user to the application automatically? Is there any ability to make the flow of Inviting by Email similar to the flow of Inviting by Id?