Clark has a post about getting used books through Amazon, and he tells us that a book he just got that way came from a library. This is indeed a sad phenomenon, this getting rid of philosophy books (replacing them with nonsense and ephemera, I'll be bound).
I have run into this myself. My copy of Jonathan Barnes's The Presocratic Philosophers (the one-volume edition, 700+ pp) came from the Virginia Beach Public Library. I wanted to send it back to them, saying "no, you keep it! What if some Virginia Beacher needs to know about Heraclitus right away??" But I didn't. Their loss.
On the other hand, they get points for having it in the first place. Our local library's "philosophy section" has an ancient (relatively speaking, that is) edition of Plato's dialogues, The Essential Nietzsche, The Will to Power, Being and Nothingness, an intro to philosophy by Jaspers, of all people (an existentialist trend here?), a dusty secondary book on Dewey I'd never heard of, a coffee table book, and ... I can't remember anything else (I'll go check). But we're a small borough – nearby libraries are bigger, and one got recent Oxford general-audience releases by Searle and Blackburn. So that's something.
I keep wanting to go to them and say: look, your philosophy section is terrible, you need these books here (presenting list). They might indeed order them. But I don't think anyone would take them out.