Oh, I remember those cards... thats nice. I mean, the memory. In fact, I saw one of them again some time recently... when I was visiting someone ... yeah, Germany. There they still used 'em. Or in that library anyway. In that department of the library.
Havent seen them in a library at home (Holland) for eons. But I used to like 'em exactly for the reason Chai described.
(In that German library, there was a book with lyrics and brief backgrounds of socialist struggle songs. It hadnt been lent out since ... the early 80s, I think. Actually, I think it was only in the music library that they still had those cards there - you know, the books with notes.)
Now the ones in Utrecht have barcodes... big fat barcodes pasted underneath an extra plastic layer somewhere unflattering on the front or back cover of the book.
Also, with the computerized databases of the books they have, and exactly when and how often they are lent out, they are being much more efficient with the collection - space is scarce, after all, downtown - so anything that they see is hardly lent out, goes on the "1$ sale" table. So new books can be added in their place.
That book on socialist struggle songs would have been thrown out decades ago.