AppleInsider quotes a Billboard report that Apple has been irritated by Amazon's MP3 Daily Deal. According to Billboard, "The labels make arrangements to provide an exclusive selling window with Amazon for a big release expected to do a lot of business on street date." In other words, Amazon gets to sell some new hot releases for 24 hours before they get to the iTunes store.

It's no surprise that Apple isn't thrilled with that. It appears to have started when Island placed Mariah Carey's "Memoirs of an Imperfect Angel" in the promotion. People could get the new album for $5.99 for a full day from Amazon before its September 29 street date--and appearance in the iTunes store.

The report says Apple has been encouraging labels to reconsider that strategy, and backing it with warnings that they will withdraw marketing support in the iTunes store for releases featured as Daily Deals. Billboard says it's working, with executives at Capitol and Capitol Nashville deciding not to participate in Daily Deal promotions they'd been considering. Billboard also reports that, "sources say that when Amazon recently approached Hollywood Records to highlight 'Who I Am,' the debut album by Nick Jonas & the Administration, the label declined."

The iTunes store recently sold its 10 billionth song (if you're the one who won the contest and $10,000, let us know!) and has been estimated to make up one-fourth of all music sales in the U.S.--by far the largest music retailer.