Thanks to the contributors, extensive quotes in IMDb including all of John Doe's and most of my personal keepers:
This however is not in IMDb but no more about library cards these days but Face Book or Google search history and email trails:
For years, the FBI's been hooked into the library system, keeping records.
- Assessing fines?
No, monitoring reading habits. Look. Certain books are flagged. Books on, say, nuclear weapons... "Mein Kampf". Anyone who checks out a flagged book has his library records fed to the FBI.
-Wait. How is this legal?
Legal. Illegal. These terms don't apply. You can't use the information directly. It's just a useful guide. It might sound silly, but you can't get a library card without an ID... and a current phone bill. See?