Anonymous Library Cards
From the article:
Source: Library Associates LibBlog
With an anonymous library card, the library is willing to loan materials to anyone because it knows it can't really lose anything. Since the library would never loan more than it could re-coup from a cash deposit, it would be able to loan controversial items without storing personally sen-sitive information. If the user doesn't return the material promptly, the fines would be deducted when it's finally checked in (or once the accrued fines reach the price of the material).