In my jurisdiction, the local transit authority keeps a database of every fare payment ever made, with no expiry policy or any other future-looking privacy measures. The records are easily and routinely subpoenaed by law enforcement, and non-anonymized datasets are shared with researchers, as long as they pinky-swear to not compromise anyone's privacy. You can pay in cash, but have to pay an extra fee for a new fare card each time you want a new unique ID.
Nobody seems to care.