Since June of 2008, Amazon has been offering customers of its MP3 store a "Daily Deal," selling a recent or classic album for a rock-bottom price. (Usually either $2.99 or $3.99, and announced each day via the amazonmp3 Twitter feed.) Well, according to Billboard, the market leader in MP3 sales—Apple's iTunes—is none too happy with the popularity of Amazon's deals. So long as Amazon was taking the financial hit and using the deals to drive traffic to their site, no one fussed much. But last year Amazon starting working in concert with major labels to offer pre-street-date exclusives and to help goose opening week sales, and apparently that's left the people at Apple questioning the loyalty of those labels. Billboard's story has more details. Fans of legal downloads should read it to get a sense of how Apple works behind the scenes to control the business. And fans of Amazon's deals should read it to understand why the Daily Deals lately have been less enticing.