The Art Of Prediction?
In his list of music industry predictions, Bob Lefsetz makes this point about digital music,
"The most interesting point is how the usage of music will change. People shoot MANY MORE digital photos than they ever did film ones. People will own MUCH more music than they did in the physical era. This is good."
He may be right, but I already sense a digital overload/ennui amongst people who own an amorphous mass of music (as opposed to a collection of CDs) and more specifically, I'm always wary of the tendency to assume all digital content is the same. People own many more digital photos because digitisation has reduced the expense of a photo and crucially eliminated the hassle of getting films developed. Neither of these factors apply to digital music.
It's important not to forget to look at the differences as well as the similarities when you look for analagous markets.
Bonus link: I never met Ahmet Ertegun but I knew all about him and his brother from co-workers. Bob's eulogy for him is a lesson for anyone wondering about how to imbue a business with passion (as the fabulous comments section all attest).