About a week before Christmas, my Wii started to exhibit some discoloration in spots of games and in the Wii menu, and then started pixelating real bad in spots as well. Doing a little research, I found that these were signs indicative of internal overheating.
I called Nintendo about a day or so before Christmas, they offered me the advance replacement plan which I gladly accepted, took my credit card, and then shipped me off a BRAND NEW Wii, as opposed to a refurb. My Nintendo rep told me that all replacements for the next month would be brand new units as they had to stockpile a certain amount of refurb units before they could start going to those.
One thing that did bother me during this process is that my rep told me up front that I would be losing any virtual console games, and that there was no way to save them. He told me the EULA you agree to when you sign up for the Shopping Channel clearly states this. At that point, I had only downloaded Bonks Adventure, and only wound up losing $5. Still, makes me mad that I lose $5 because their console was defective.
Reading the Wii technical forums for awhile, it seems that a lot of other people were having issues similar to mine. The general consensus was that the people that were having overheating issues had their Wii placed in a Horizontal position, and had Wii 24 connect turned on, and standby mode on so that the Wii never turns off.
Apparently when in standby mode, the Wii uses only slightly less power than when on and running, which seems to be the issue. When the Wii is on and running, the fans are activated and funnel out the hot air. When in standby mode, the Wii is using slightly less power, which means it is generating heat, but has NO way to activate the fans to cool the console down if it gets hot. People also seem to think that the Wii gets better ventilation in the Vertical position using the stand than not. I don't understand that theory at all, but it's out there.