Roger Paget took up some interesting themes this morning. His genealogical journey has taught him a lot, about this country, about the state of the art (many new tools, swift improvements).
So how shall we balance historians prying, wanting a complete picture, against the requirement for secrecy? In the case of ancestors, it's not that hard: the skeletons in the closet come out only long after the fact, and only with concerted digging -- they wait for the right historian.
But the security-minded often want access to stuff in the present, don't want to wait for some decent amount of time to fly by (the security-minded might not live that long either, eh?).
On the other hand, a lot of what marketing and medical researchers want is reliable anonymous data. They actually don't care to know who, don't need to know who, in order to do their jobs. Some police work is quite different obviously (not all of it though).
The technique of using pseudonyms to mask case histories, thereby providing doctors with true stories, yet fake identities, is an ethical one, and important to medicine.