Is it already clear what would be done in case person A's information has been sought, but person A has no other communication methods available other then talkpage? Would this mean the notification would be posted there? (I guess I would not very much appreciate posting that kind of things to my talk page, but maybe others think otherwise of it) I assume it is a detail, but not something that would occur very rarely I guess...
talkpage is not notifying a person, but notifying whole community. the real valid way we have of notifying people is by email they specify in their account.