There are 225 million iTunes account holders. 25 million joined in the three months. As the iTunes store has been operating since April 2003 it’s possible to step back and look at its history and measure the rate of growth relative to other ecosystems.
The following chart shows various platforms/ecosystems in terms of adoption. In the case of phone operating systems and consoles, the cumulative units sold is shown. The scale is 10 years by 1 billion users with users measured on a logarithmic scale.