The Wii is an external device that you plug into your TV's input ports. The only possible way, and this is a long shot of course, I can see the Wii harming your TV at all, is if you were to leave it on for days, upon days. Then it might burn images into your TV's screen, etc... But even this is unlikely, especially an HDTV and all, plus the Wii has it's own Burn prevention setting thingy.
I can't really find anything to prove this... but it's kinda common sense. There's no way your Wii, or anything like it (like a DVD player, VCR, other game consoles, etc...) could harm your TV like that. I understand the hesitancy, since it's an expensive TV and all, but I think you guys can rest assured the Wii will not harm your TV. =P