
The Long Tail theory is about how the niche market can make just as much money as the mass market. e.g when a song first comes out (paparazzi) loads of people would buy it from the shops and then in 5 years or so not so many people might want to but it and so shops would stop selling it. Now you would be able to buy it online from a site like play.com, whereas before you would have had to see if you had any friends who had it that you could buy it off or borrow it from.