Turns out that the music industry has complaints of a more litigious nature. From Reuters:
A new Amazon.com Inc service that lets customers store songs and play them on a variety of phones and computers is facing a backlash from the music industry that could ignite a legal battle. Amazon's Cloud Drive, announced on Tuesday, allows customers to store about 1,000 songs on the company's Web servers for free instead of their own hard drives and play them over an Internet connection directly from Web browsers and on phones running Google Inc's Android software. Sony Music, home to artists such as Shakira and Kings of Leon, was upset by Amazon's decision to launch the service without new licenses for music streaming, said spokeswoman Liz Young.
Because what the music industry really needs right now is a costly legal battle with one of the largest online retailers in the world (who, by the way, are trying to make it more convenient for you to listen to your music). Oh, music industry! When will you ever learn?
Update: Billboard has an interview with Amazon's director of music explaining why they don't believe they need music licenses for the service.