Years ago, the very thought of downloading music from Apple was ridiculous. But in a relatively short amount of time, digital downloads have not only increased at a rapid rate, they have taken the world by storm.

Nowhere better is this exemplified than in the news from the Apple camp today, claiming that iTunes has taken the second-place spot in US music sales.

iTunes has officially supplanted big-box store Best Buy at second place and is now within striking distance of Wal-Mart to become the United States' top music retailer, according to Apple. The company claims it has sold over 4 billion songs worldwide and has an astounding 50 million iTunes customers.

50 million... and counting

"We'd like to thank the over-50 million music lovers who have helped the iTunes Store reach this incredible milestone," said Eddy Cue, Apple's vice president of iTunes. "We continue to add great new features like iTunes Movie Rentals to give our customers even more reason to love iTunes."

Apple did not release any worldwide figures. But given its success in the US and general lack of competition worldwide, it's likely to be experiencing the same kind of success elsewhere.