The physical space is a big one, I think. There are many ways a library could be "replaced": Wikipedia, content piracy, cheaper home Internet and so on. But simply having a physical place is something Google cannot give you. That's why library architecture is such a huge part of the literature, I think.

But based on our numbers and the community research we've done over the years, I think it's still physical materials the drive the bus. People like stuff, real stuff.