here is an excerpt ripped from mariokartwii.com
its a discussion between a user and a nintendo spokesperson... read
Me: First of all, is MarioKartWii.com at all affiliated or supported by Nintendo?
Nintendo: No. The official website is Mario Kart Wii . If you ever want to make sure a website is sponsored by Nintendo, we recommend that you access Nintendo's main website, select a game, and the official sites for that game will be listed.
Me: Now that you have read the first post of this Custom Tracks topic, is this something that Nintendo approved or supported?
Nintendo: No. We never support illegal software of this sort. Unfortunately, with the internet, this sort of thing happens, but we don't recommend or support this.
Me: Is there any risk of voiding our Nintendo Wii console's warranty by downloading and installing any of these software files?
Nintendo: Yes. Anytime software or files of an illegal nature like this are used on a person's console, their warranty is voided.
Me: Well, I know in the old days people would hack their consoles by manipulating the actual hardware of the system, you know? But that isn't the case here. This is completely downloaded through a person's SD card that is inserted into their Wii. It has nothing to do with the hardware.
Nintendo: Software exclusive hacks still void the warranty. I mean, Nintendo will still repair consoles that have fallen off a tv stand or [laughs] been run over by your car. But when a person sends in that console and something like this [Riivolution] is on it, the customer will be stuck with a broken Wii.
Me: Is there any risk of being banned by Nintendo if caught using any of these software files?
Nintendo: Yes. Someone who is caught using this will have their account suspended. So, when they attempt to log into Mario Kart Wii, for example, they will get an error message about not being able to connect. They will need to call us up at that point and talk to a representative about getting unbanned.
Me: I know Xbox has started disabling consoles so they can no longer go online in general. Is there any risk of consoles being disabled by Nintendo like that?
Nintendo: For about..close to...a year now, we started to disable consoles' ability to go online. They will get an error message when attempting to.
Me: In general? Not just for a specific game?
Nintendo: Yes.