Wired's Listening Post blog is theorizing that the current spat between Universal and Apple is because Universal wants a piece of iPod sales.

Here's the money quote: "In addition to gaining more freedom to set deals with iTunes rivals and possibly renegotiate prices, UMG may be angling for a cut of hardware sales. Microsoft pays the label a $1 fee for every Zune portable music player it sells. It's unlikely, however, that UMG would be willing to throw away the majority of its digital music sales by pulling its catalog from iTunes entirely."

That sheds some new light on the situation. In any case, the blog points out that Apple also has a lot to lose here, not just Universal. So it's in both companies' best interest to work something out.

Music Label iPod Tax Behind Universal-iTunes Standoff? [Listening Post]