Ambient light doesn't. We would have heard something by now.
The issue is that the wii-mote and receiver strip work on a particular frequency of light (not sure what, but let's say infra-red, like a TV remote). Direct sunlight contains all known frequencies of light, but reflected sunlight, or artificial light, do not. I remember some TV remotes not working well when direct sunlight was shining on the little IR receiver. This is nothing new, and it's not a problem that's unique to Nintendo's product.
Nobody cares much that TV remotes don't work when strong sunlight is shining on the TV, because nobody watches TV with direct sunlight on the screen anyway. Nor do they play video games under those circumstances.
You won't have to sit in a dark room, Spuds, you hate-mongeror. I can't believe how easily you just sold your intelligence and integrity to jump on a bit of negative info about Wii (which turned out to be nothing). You really are an idiot.