Retrieve customer information from an iPhone app purchase transaction

Apple clearly states in its Discover the Store video in the iPhone Dev Center that we must:

"Save a copy of the TransactionID along with the Client Information on your server to the cloud. That way, if a client mistakenly uninstalls your application, you have a mechanism to recover. You can check your server the first time you run your application to record a purchase for that client and return it. the application is in its state before it is removed. Trust me, customers will be grateful! "

Fine! Now, I haven't worked with In App Purchasing yet, but when looking at the In App Purchasing Guide, I don't see how and when the Store Kit provides access to any "Customer Information" in the app. So, I think we need to bother our customers for this information, whether we use in App Purchase or not, given that Apple does not give us any access to the vCard in their address book that contains this valuable information.

Are my assumptions correct? In order to be able to recover after deleting an app after purchasing an app, do we need to obtain unique information from each user to log into our servers during each purchase?

Edit: We'll be looking at an inline product model with in-app purchases.