There's a great red herring flying around the net based on the single datum reported at itunesperipod.com. Everyone seems to be using it for their own purposes (links go here).
Many people have assumed this means people are pirating music left and right. In my case I've bought more than 21 songs on iTunes, but it's only a small fraction of the music on my ipod. The top two classifications (by far) are a) music I bought on CD and b) music from archive.org and other free concert download sites.
Also, I like to own my music, not rent it, in case you wanted to use me as an example of other purchase models.