You’ve seen anonymous cash cards already; you may even have received them before. They’re better known as gift cards. Using the same principle, libraries can issue a borrower card that uses cash, rather than personal ID information, as collateral. Here’s an example: If a privacy-minded user deposits $20 to get an anonymous library card, she can check out The Terror State without identifying herself. Her account balance is temporarily reduced by $15, and when the library checks the CD back in (in good condition), her balance is restored to its original value.
That’s one way to get around the Patriot Act!

Anonymous Library Cards Allow You to Wonder, ‘Who Was That Masked Patron?’