Where there's a will...

Well, that didn't take long. Gizmodo has step by step instructions for defeating the DRM used by the Zune for wireless sharing of music - use the image hole:

First, you need to enable hard drive mode using the instructions we posted before. Then, rename whatever files -- MP3s, movies, programs -- to have the extension ".jpg" in order to fool the Zune into thinking its an image. This hack works because Zune doesn't apply DRM to images!

Then you just rename them back on the host PC and synch them back to the Zune. I should start an over/under pool for how short an interval it will be before a "critical" update comes out to "fix" this.