mouse_clicker, They don't have to pour money into it. It doesn't cost a ton of money to run a match-making service that points two or more gamecubes at each other. They probably could do it with the existing resources at nintendo.com. If they really need to cover any extra expenses they could charge an extra five dollars per on-line capable game.
I agree, Mario Kart co-op is a blast. It's even more fun when you have a large group of actual human beings controling all the characters. Unfortuantly Nintendo wants the only way you can play that way to be if you have 2 GameCubes ($100 each), 2 copies of Mario Kart ($50 each), 2 Broadband adapters ($50 each), 8 controlers ($25 each), and 2 TVs (hopefully you already have these ). That's a grand total of $550. Good for Nintendo sure, but bad for you. Actually it's bad for Nintendo too, because in the above senario, no one is going to buy the Broadband adapters to do all this. Not that they make it easy to get one as it is.
Silks and nolimit19, I don't think a monthly fee service will ever work in the long term. No one is going to pay ten dollars a month to Nintendo, Sony, and Microsoft. That would be thirty dollars a month, $360 dollars a year. At best they'd have to choose one. Which would still be $120 a year.
Hostile Creation, great you're not interested in on-line games. In case you hadn't noticed, lots of people are interested in on-line games. I guess none of those people matter because they're not you.