Even though it seems that everyone has some sort of digital music player, iPod or other, the market is still wide open with plenty of room to grow.
Household penetration of MP3 players (not just iPods) in the US is about 15% making it one of the least popular consumer electronics devices but still ahead of digital TV sets, Pagers and home fax machines. This also puts iPods behind such consumer electronics as LCD TVs and satellite TV systems.
A good comparison is between MP3 digital music players and DVD players. In January of 2001 DVD players had a 15% market penetration but as of this year they are in about 75% of US households.
According to the Consumer Electronics Association that some 7 million MP3 digital music players were sold in the US in 2004. CEA also speculates that another 10 million will be sold this year in the US. For another comparison, look at other portable audio devices, such as portable CD and tape players. These lower tech devices sold double the number and will do again this year even though their peak was in 2001.
For the full story:
Forbes - When IPod Sales Run Out Of Steam