There was a discussion on diglib a while ago about what is a digital library. This was more interesting than most, especially when it came to Eric Hellman’s question about whether particular services counted as digital libraries or not.
A digital library is “Any collection of digital resources managed with the primary goal of maximizing the collection’s utility to a defined user community”. [firstname.lastname@example.org]
Libraries are not ends in themselves, but serve the interests of the organizations of which they are a part. As university emphasis varies around research, education and career poles, we can expect to see libraries evolve to support those emphases more strongly.