You misunderstood -- or I didn't make myself clear -- on "mature market." A mature market doesn't have to do with the age of the consumer, but the number and types and price of units out there.
I know but my point is even with other options young people are still going to want the "cool" one and that is hands down the iPod. And later on people will stick with the iPod because that is what they know. Apple also has an advantage by having a store on most campuses. Students can charge one to a bursar and pass the student discount on to their parents. Why go for a knockoff when you don't even have to pay for the best one?