First Vivendi shifted its weight away from Mr. Jobs, and now NBC is following suit. Rivals from MTV and Amazon.com, EMI and Wal-Mart are also nipping at the digital music titan’s heels.

Per Reuters: NBC decided not to renew its contract with iTunes, pulling Battlestar Gallactica and Heroes from the teeny-tiny screen and becoming the second major media company to challenge Apple.

Per the The New York Times: MTV last week said it was going to fold its digital music service into a venture with the owners of the Rhapsody, “as part of a renewed challenge to Apple’s market-leading iTunes store.”

Per the Financial Times: “NBC appears to be embracing a rival. The media group, owned by General Electric, has begun to sell digital downloads through Amazon.com, the online retailer that is gearing up to challenge iTunes.”