Wii Scratching Disks
Solution 1:
This person on the Tilted Forum Project forum seemed to get lucky with Nintendo's Customer Service. Try contacting them.
As to trying to prevent the problem, is your Wii mounted in the vertical orientation? According to some websites, placing your Wii horizontally may reduce the scratching of the discs.
Solution 2:
I would suggest to contact Nintendo Customer Support, as this seems like a hardware problem with your Wii unit itself.
During normal operation, the Wii should not scratch disks, especially not with a perfect circular. (unlike certain Xbox360 Models)