I think it's actually signed for a specific console, not just a serial somewhere in the header or something. The files are encrypted.
It's nintendo though. It will be done eventually. It's just a matter of what part of the system will be broken first? The firmware? My guess is the drive will be hacked first, via a method simillar to the xenogc or duo-gc. The wii discs have a barcode just like gamecube ones (identical to the eye), and the console still gives that little "beep" sound when the barcode is confirmed, and the disc authenticated.
For those who don't care about wii, the fact that it's basically a gamecube is a good point for ridicule. For those who want the wii hacked, the laziness/cheapness of nintendo will come in quite handy, I'm sure.