Note the difference between sales share and in-use share of the market. What you see in the street is what people keep and use. Sales share (boxes sold) is what the analysts measure (and usually only sales through particular channels).
Of course this can cut both ways. A device kept in a drawer counts as a sale but is invisible. On the other hand, someone who buys a new iPod every year counts as lots of sales, but he's still only carrying one around to be seen...
Cheers
-- perry
If You Were Wondering, The iPod Is Officially "There"