Arguably, payment systems themselves (credit cards) are the richest, most deterministic, and among the largest data siphons available.
Back in the late 1990s a friend working for the leading back card reported a conversation with another worker with defence experience. Defence's was talking of how an IC associate expressed jealousy over the size of the bank card's data trove: "you've got more information than we do".
I'm unsure how reliable this is, or was, but the conversation was at least a casual acknowledgment of the possibility at the organisation.
Back in the late 1990s a friend working for the leading back card reported a conversation with another worker with defence experience. Defence's was talking of how an IC associate expressed jealousy over the size of the bank card's data trove: "you've got more information than we do".
I'm unsure how reliable this is, or was, but the conversation was at least a casual acknowledgment of the possibility at the organisation.