Apple touts that based on the latest NPD Group’s Music Watch the iTunes store has surpassed Wal-Mart to become the number one music retailer in the US.

"We launched iTunes less than five years ago, and it has now become the number one music retailer in the world,” said Eddy Cue, Apple’s vice president of iTunes. “We are thrilled, and would like to thank all of our customers for helping us reach this incredible milestone."
The number 1 ranking of the iTunes store is based on data from market research firm the NPD Group’s MusicWatch survey that captures consumer reported past week unit purchases and counts one CD representing 12 tracks, excluding wireless transactions. The iTunes Store became the largest music retailer in the US based on the amount of music sold during January and February 2008.

The iTunes sales amount is directly correlated to Apple iPod players on the market. The Apple stock is trading above $150 again, looks like there is no slowing down for Apple in sight.
Via the Apple site.