What's more important? Which should the library be more concerned about? The quality of its materials or the demand of the masses? It's not an either/or. Both are important.
Libraries are not going to bring people in if they are focused solely on quality. Not everyone wants to read the classics. This would result in a feeling towards reading that many students feel in the classroom. Forcing students to read Melville, Shakespeare or Faulkner is not going to get many interested in reading. If the choices in the library for adults are along the same lines, then their views of reading will never change. Reading is important for reading's sake alone. Being able to engage the mind through reading is important. As Ross mentions in her article "Finding Without Seeking," even readers who read "fluff" are engaging their minds and learning. They are relating to characters or seeing a different view of the world. Just because they are not getting this reaction through classics does not diminish the effect that that reading experience had on them. Isn't opening peoples' minds to different view points, even if they're fairly minor, good for society as a whole? Isn't helping people engage their minds a public good? If libraries can reach people by listening to the demand, then there is nothing wrong with that.
On the flip side, however, there is something to be said for quality. Many classics have become a part of our shared knowledge, our culture. It's for the public good for a library to help in maintaining that. One of the students in another class is an elementary teacher. She had mentioned that she had asked her class to name some fairy tales. The only tale that anyone in her class could name was Shrek. They couldn't come up with Cinderella or Little Red Riding Hood. That's incredibly sad to me. These fairy tales are shared knowledge in our society. If the next generation does not know them, what does that say about our society? About our culture? To me this is a prime example of the importance of the quality in the library. These stories may not appeal to patrons on their first few trips into the library, but as readers' advisors, we can eventually show readers quality materials that we think they'll enjoy. Use the demand to bring them in, so we can introduce them to the quality.
So, yes, I believe quality and demand are both important for a library. The trick is to find the balance. This can be difficult when there is limited space. But I believe it's important for a librarian to remember the importance of both sides of this argument because they are both quite valid.