What personal information does Nintendo have access to via the Wii?

I've been thinking about this a lot in relation to Facebook, etc, and then I got to wondering how much data Nintendo gets about us through Wi-fi and the network apps. It *seems* like it would be less than many web sites given that we're just playing games here, but then again--this is information about how we're spending our time, potentially how fit we are, etc. I'm having this nightmare scenario where insurance companies are watching our scores on Wii Fit and adjusting our rates accordingly. <chills>
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