Well in Australia we have what used to be called statutory warranties, and is now called "consumer guarantees", and it's a statutory right that a consumer can't waive, and that can't be negated by other warranties. In essence it means that retailers and/or distributors/manufacturers have a responsibility to repair/replace/refund for the "expected life" of the product. If you buy an "extended warranty" in Australia, you're essentially an idiot because it gives you very little extra on top of your automatic legal rights to expect the product will be repaired, replaced or the depreciated value refunded for the life of the product. Believe me if Nintendo did it to their Australian clients, there would be multiple threads on the whirlpool forums about it. Apple have a page
here that explains it (really poorly IMHO) for their customers. Nintendo explain it even more poorly on
their website:
"In Australia, our goods come with guarantees that cannot be excluded under the Australian Consumer Law. You are entitled to a replacement or refund for a major failure and for compensation for any other reasonably foreseeable loss or damage. You are also entitled to have the goods repaired or replaced if the goods fail to be of acceptable quality and the failure does not amount to a major failure."
Notice that they can't even say, legally, that opening the wii and installing a mod chip voids your consumer guarantee - because it doesn't. It doesn't stop them, however, from making that claim
on this page here, and the claims that they make are both factually wrong and they would loose in court just like Sony did in 2005, but potentially libelous as well. As such they haven't even tried to bring suit against mod-chip distributors in Australia. Nintendo did win a case against the sales of the D4 flash cart, but that would have been for different reasons (tradmark/patent infringement, etc).
Now to get back to your situation, in the USA. As I said, check your local laws. I see on Nintendo of America's page
here it says this:
SOME STATES DO NOT ALLOW LIMITATIONS ON HOW LONG AN IMPLIED WARRANTY LASTS OR EXCLUSION OF CONSEQUENTIAL OR INCIDENTAL DAMAGES, SO THE ABOVE LIMITATIONS MAY NOT APPLY TO YOU.
And this:
This warranty gives you specific legal rights, and you may also have other rights which vary from state to state. Nintendo's address is as set forth on the back cover of this booklet.
They're not going to tell you what you're rights are, going by the information on the Australian site which makes it seem as if installing a modchip voids your rights under the consumer guarantees, etc. Check your rights, I already know what my rights are and I know that if Nintendo tried to stiff me like they did to you that I would politely call them and explain that the homebrew software is none of their concern and doesn't alter the fact that they have an obligation under the Australian Consumer Law to sell a product of merchantable quality that is covered by a an automatic non-waivable consumer guarantee. I would further inform them that any further inaction on their behalf would result in me posting the story for other consumers on the Whirlpool.net forums, giving other peers the opportunity to discuss whether you have acted appropriately under the Australian Consumer Law.