It hasn't surprised me that someone has done this, but I'm still quite excited about it.
A guy by the alias "ChipD" has successfully managed to add a second NAND chip to the Wii, flashed with a backup of his Wii from his original NAND chip.
Using a 2 NAND chips piggybacked on eachother salvaged from a USB flash drive and a switch, he can now change between two different NAND chips allowing him to effectively have 2 Wii's inside one unit.
But be warned, this mod is extremely tricky and requires soldering pins the size of a hair, so it's not for beginners.
Potential uses? No more sharing the Wii with your family, store more VC games on your console without having to delete them, homebrew development, and so on.
It hasn't surprised me that someone has done this, but I'm still quite excited about it.