iTunes now number two music retailer in U.S.

Computing giant Apple announced its iTunes digital music storefront is now the second largest music retailer in the U.S., trailing only traditional retail behemoth Wal-Mart, according to data released via market research firm NPD Group's MusicWatch survey. Apple reports the iTunes Store now boasts more than 50 million customers and total sales of over four billion song downloads, including 20 million songs sold on Christmas Day 2007 alone.  

For more on the iTunes juggernaut:
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