July 31, 2007
3 Billion Songs Sold
The world’s most popular online music, TV, and movie store, iTunes features a catalog of more than five million songs, 550 TV shows, and 500 movies, and it recently surpassed both Amazon and Target to become the third largest music retailer in the US.
(link)
Note: They got to 1 billion on February 22nd, 2006, shy of three years after they launched; then reached the 2 billion mark by January 9th, 2007.