Tom directs to an Utne Reader Article on Libraries .
This being the Utne Reader, there is quite a bit of stuff (and nonsense?) about de facto censorship in the modern library. What they appear to mean by this is that the community doesn't use its funds to acquire, catalog and display a wide array of niche materials.
Ask young people about libraries. Do they expect to find recordings by indie bands or periodicals like Maximumrocknroll, Punk Planet, Venus, or Razorcake? Ask new immigrants. Can they find recorded music or community papers in their languages? Ask Neo-Pagans. Can they read Reclaiming Quarterly, PanGaia, and newWitch?
While it's perhaps regrettable that our libraries do not retain shelter publications for every varied interest under the sun, the fact is that funding is limited. Most library patrons aren't aware that a large number of new-release popular materials are actually rented from a clearinghouse. If you see a green sliptag under the plastic-wrapped dust jacket, the book is not owned by the DCPL system.
One of my favourite pastimes at my old job was reading this magazine. You'd be amazed at the amount of time and energy spent by modern acquisition librarians as they tailor collections to the needs of the community which funds them.
UPDATE: I couldn't remember the name of the rental program, so I asked the Library. It is called McNaughton and their website is very interesting, if you happen to be a library geek.