In order for users to trade songs with one another, they need to subscribe to Microsoft's mobile music service called Zune Pass. This service costs $14.99 per month and allows the user to download any of the 3.5 million songs in Microsoft's library to their Zune. A contrasting payment policy when viewed against Apple's $.99 per track option.
Of course many researchers believe that Apple's dominance in the portable media player market is far too strong for any real competition to be formed. Only time will tell if Microsoft's new direction takes away any of Apple's 71% market share.