The three major labels control 75% of the music sold in the U.S..
Apple already controls 70% of the music download business. Until now all music download services launched by other companies like Microsoft have not been able to compete with iTunes head to head.The effort by Universal might be successful especially if the rumored business model of all-you-can-eat music for the end consumer would be true. Apparently Universal would charge a subscription fee that they think carriers and hardware makers would pay. I am not sure if this is really feasible.
More details on Business Week.