Universal may not renew their contract with Apple to sell their artist's music on the iTunes Store according to The New York Times' Jeff in Apple Faces Rebellion Over iTunes:
The Universal Music Group of Vivendi, the world's biggest music corporation, last week notified Apple that it will not renew its annual contract to sell music through iTunes, according to executives briefed on the issue who asked for anonymity because negotiations between the companies are confidential.
Apple has a well-documented stance on not wanting to raise their 99-cent per track price while the labels badly want a price increase. iTunes' incompatibility with non-Apple media players is also likely to be contributing to the rift.
Universal artists include Gwen Stefani, 50 Cent ,Marian Carey, U2 and Kanye West and they also own a number of sub-labels, including: Def Jam Recordings, Geffen Records, Interscope Records, Mercury Records, Polydor Records and A&M Records.