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It depends on the retailer, my local newsagent (Oyster Ticket Stop) won't add Oyster Photocard numbers to a card, but the one down the road will.
The last time I tried to add a Bus+Tram photocard at a tube station, the booking clerk claimed I hadn't had my name and address added to the card, despite the card being registered, he called his supervisor who then allowed him to add the number but asked me for my address.