This didn't happen to me with the Wii, but it did happen to the Gamecube.
It started when I've found out my Memory Card got full (the one I've got with the Gamecube), so I've been looking at the internet for another card, and I've found a 3rd Party Memory Card with lots of more space on it, and brought it.
3 weeks after moving all of my Gamecube data, the new Memory Card forced me to format the card, in order to continue playing any game.
Then I was mad!
I thought, no more *bleep*ing 3rd Party junkware!