If you're on twitter and you're a book person, you probably follow @glecharles, aka Guy LeCharles Gonzalez, the LoudPoet. If not, you should.
Here's a bit from a recent post from his blog:
Beyond all of the philosophical reasons to support libraries, there are three very concrete reasons I can think of:
Discoverability: With the volume of books being published each year growing exponentially, it’s increasingly difficult for any book to rise above the noise and connect with its audience. While “curation” is the buzzword du jour, librarians have been curating books forever, and there are far more libraries than bookstores in this country. Most library websites are better than your average independent booksellers’, too, and as ebooks become increasingly popular, being visible on more than Amazon, B&N and Goodreads will be a critical advantage. As ebook business models evolve, direct partnerships with libraries become an option, too, like the recent innovative deal between the Colorado Independent Publishers Association and Douglas County Libraries.
Digital Literacy: Libraries aren’t warehouses for books and movies, they’re often the only resource for people in their communities to learn about and interact with new technology. Only the most cynical of publishers can believe there’s no value in nurturing new readers, and libraries have long been invaluable in that regard. Today’s borrower is tomorrow’s buyer, but only if they have equal access.
Diversity: Library collections tend to be more diverse than bookstores because they are community-oriented, not driven by commerce. Beyond the bestsellers and trends du jour, libraries can connect readers with books that “the market” has pre-determined to not be commercially viable.