About 25 years ago, I struck up a conversation with a visionary, slouched across from me on an L.A. bus. The guy was in his early 20s, but he spoke with the wisdom of age as he addressed the digital revolution that was then in its infancy. "One day," he said, "you'll be able to have music delivered right to your home through your telephone line. It will all be done through little computer chips. All you have to do is just call up the record store and place your order." He was partly right. Today, you can receive music...