Omg wii demos is almost impossible
People think the wii can hold an entire demo
The wii is a not like the 360 were you can download millions of games. The wii has only roughly half a gigabyte of memory, not even close enough to an entire demo.
But then people say "just put it on the sd card". Think about it. People will be able to hack into that with extreme ease.
Nintendo will most likely never put demos on the wii, unless it comes in the form of a wii demo disc.