What is the library of the future? Let me try to reformulate the concept of the library in a vision.
Just as Last.fm is a social network oriented around music or WeRead.com is about reading, library is a social network oriented around knowledge. It is a social organism, so it grows and evolves, just as other organisms do. It is not a machine. It is also an open system in which both its input and output are free. And finally, library is a knowledge technology, it's a way we "know" stuff.
The important collections libraries have are not made of books, but made of people. There are lots of different carriers of knowledge in libraries: books holding knowledge on paper, databases containg knowledge in bits, people having knowledge in heads. People are the most important carriers of knowledge. In them, there's the social and knowledge capital libraries have.
To start social interactions library enables communication in an open, transparent way. Building on top of that, library enables conversation, that is a communication within a set of people known to each other. Library is designed to connect users. It helps to connect expert users within a specific domain. Library provides access to knowledge but also provides access to the holders of knowledge. It offers information services but also enables its users to offer information services to each other.
This is similar to the difference between centralized and peer-to-peer services. Centralized services (such as Napster) have one central source (server, repository) and are therefore highly dependent on it. Peer-to-peer (P2P, such as Skype) model uses multiple distributed sources so the overall function of a system is independent on any of its constituent parts. Library is a peer-to-peer system because it not only offers its own sources and services but also provides a social protocol for users to offer to each other resources they control and services they are able to supply.
Library doesn't organize knowledge but empowers its users to organize it. It enables users to create knowledge in a way so that it can be shared. Public knowledge interactions are recorded and stored for re-use. In this body of recorded knowledge there are explicit links that can be followed. These links make sense because they have meaning. The meaning of link is defined by how it's being used and this meaning is encoded in the link in a structured way. Library enables to link everything and in this way attach a description.
The borders of a library are not clearly defined, so no one can say where it begins and where it ends. But library has a well designed space that it can offer to its users. It provides a habitat for knowledge interaction. It's an environment designed for social interactions and knowledge exchange. In this respect, library provides lots of affordances, it's an opportunity-rich environment.
Library provides an intriguing interface for its users. One part of this interface is the interface for the library, the other part is the interface for interacting with other users. Yet, the interface to a library is transparent for its users. Users don't come to realize that they're interacting with a library. Because it's barrier-free it makes the institution in library's core invisible.