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If it's a cost-cutting operation, it might be related to the poor Wii U sales. If they're doing it in the hope Wii owners will buy a Wii U, I doubt that will work. I have a Wii and I never played online with it, so some users won't even notice the difference. People who will miss online play have to buy a new system and new games, so there is nothing that binds them to Nintendo. And since Nintendo was the one who switched off the online component for a system that was sold less than half a year ago, I don't expect they'll get much loyalty from those users.