Sharing is what Microsoft thinks of as the Zune's Killer App: the ability to beam a media file to your friend's Zune. My immediate thought was, "who wants to share?" I typically use my iPod on planes and subways and in the gym when I want to shut out other people, not invite them into an orgy of audio swapping.

My tests of sharing between two Zunes were thwarted by Microsoft's new Digital Rights Management (DRM) software. Even though I purchased music from the Zune Marketplace, and even though I was willing to abide by the DRM's restriction of allowing three plays of a shared song within three days, half the songs I tried to send wirelessly were rejected because, according to the Zune display, I lacked the rights to share those songs. Asked about this, a Microsoft spokesperson said DRM is complicated and that not all artists and labels adhere to the three days and three plays guidelines. Basically, you don't know what the rights are unless you right-click to check every song.

On the positive side, if I rip my own songs into MP3 files and add them to the Zune library, I can transfer them without restriction. On the negative side, the new DRM won't work with songs you might have bought from MSN Music, Napster or other online download sites that employ Microsoft's earlier DRM solution, "Plays For Sure." The irony would be funny, except that people who trusted Microsoft before are now going to get burned if they go with the Zune.

Kudos to Microsoft for adding wireless sharing to the Zune, a feature that the iPod lacks. But until it works, and works consistently, and comes up with something better than the 3/3 restriction, it's hardly a Killer App for me.