The Apple iTunes Music Store is now the #2 music retailer in the world, behind WalMart. This figure is for all music including CD's, not just digital music. According to the article:

It was only eight months ago that iTunes passed Amazon to become the number three music retailer. Wal-Mart is still holding its own with a massive brick-and-mortar retail business in addition to its online music store, but must be getting nervous as iTunes continues to close in.