Although the Wii was originally thought to be region-free, it's since been proven in every game available so far that games will only play on the system of the same region. If you bought a US Wii system you can ONLY play US games on it and vice versa. Japanese Wii games will ONLY play on a Japanese Wii and UK games will ONLY play on a UK Wii.
And as for Jacob's question, that really should have been the FIRST question on the list. : ) I would have know about water intoxication as I remember a runner years ago near here that dies from drinking too much water. Up until then I had never heard of drinking too much water killing you. I feel sorry for her family and she was only trying to do something nice for them. Shame. And Nintendo needs to get their ass in gear and get those systems out. Reggie's promise for "No Shortages" isn't coming true. I can't believe they're still so hard to find. I'm very glad that I preordered one and got it on launch night now. Didn't think much about it at the time as the PS3 was supposed to be much harder to find. : )
Oh and one more thing...anyone that owns a Wii needs to go NOW and grab Wario Ware Smooth Moves. Best game out for the Wii so far. Amazing!