So you can actually store and run Wii U games from an SD card.

[sethnintendo]

I thought SD card slot was mainly for the people that did the Wii - Wii U transfer. Since the Wii channel still has the SD channel on the Wii U this allows people that bought a shitload of VC/WiiWare games to be able to access them from the SD channel (since they set aside the same space (512 MB) for the Wii channel.