I doubt information would be stored on the controller, with everything else they have to fit in there. More likely, there would be a profile in the Wii24 service and the controller would just have a custom code. Imagine if you could have your games saved online, and then go to a friend's house... eliminating the need for memory cartridges. Obviously it couldn't work for every game, but the sheer coolness of just pointing the controller at the screen, hitting home, and having all your game profiles and most of your saves load...
Come to think of it, this sounds a bit like a possible final secret. Hmm...