I've recently been involved in some planning meetings for our new Campus Calgary Digital Library, and one idea that came up was whether we'd move older materials to storage, and someone mentioned how tough that makes it to browse and thus invite serendipity. I realized (not for the first time) that this is one of the major shortfalls of library service to distance students; we can send them anything, but they still can't really browse the collection (short of scrolling through titles in the catalogue).
The latest issue of Educause Review is out, and it contains a short article addressing this problem: Browsing Library Collections: From the Shelf to the Online Catalog. Robert Kieft from Haverford College discusses a consortial experiment where several institutions are physcially scanning the TOC and several additional pages of older works which are then removed from the collection. The scans are then made available in the bib record of the catalogue so patrons can better decide if this is relevant material.
Robert notes that Google Book Search and the Open Content Alliance may make this an experiment in futility, but I like the idea of integrating the TOC scans in the bib record (making the info available to your local patron as opposed to making your local information available to the world at large, as would be the case with any library info in GBS or OCA).