I have the same issue with Zelda. I noticed this concern Sunday in forums, so I checked all my discs and my copy of Zelda has two pretty severe scratches. With that said, none of my other games were scratched (and we have played Wii Sports far more than any other). Knowing that I can't return the game to WalMart (policy to not accept returns for opened games), I wrote a letter to Nintendo yesterday and have not received a reply. I truly believe that this was a problem with the disc itself and that it was not caused by the Wii system. As noted above, the scratches were not circular (caused while the disc is spinning) and not straight across the disc (as I would expect on inserting or removing the disc). One goes at an angle, and the other is almost a square spot where it looks like it has been gouged.
As it is, Zelda may be the first game that I will actually end up paying over $100 to play, as I fully expect to have to buy another copy.