The mobile music industry has a lot of players, many of which are well established: Apple (NASDAQ:AAPL) and Amazon (NASDAQ:AMZN) provide devices and music libraries; Pandora, Spotify and Rdio offer streaming music services; there are operator-run initiatives like Leap Wireless (NASDAQ:LEAP) subsidiary Cricket's Muve Music; and device-specific initiatives such as Samsung Hub and Nokia (NYSE:NOK) Music continue to expand. Yet, as with many segments of the wireless market, the mobile music industry is poised for upheaval. Rumors continue to hint at a wide variety of companies planning to enter the digital music market or existing players poised to expand their offerings. As the market continues to grow, it's worth taking a look at the key issues that are hounding the development of the market and the dynamics that could affect both existing players and new entrants. For more on how the mobile music industry is changing, check out this FierceMobileContent special report.