Librarians have traditionally been concerned with preserving and providing access to formally recorded knowledge. This is just as important as it has ever been. However, an additional responsibility today is to provide access to the informal ideas and communication channels that are plentiful on the Web. We should not become too rule-bound as we do this, or we could miss the potential of the Web to link people to knowledge.
In short, we should be less like orchestra composers and more like jazz musicians. We'll still make beautiful music.
