Have you ever turned off your console while saving a game?
The first time I did was when I was 11 and playing Kirby: AriRide and lost ALL my data on my GameCube memory card, which was well over 40+ hours of gameplay.
Well that, was the first time, the last time was last night!
I was on my PlayStation 2, jamming out on Expert mode for Guitar Hero III, and then I was eager to watch an episode of Metalocalypse, and I usually ungplug my PS2 when I'm done playing but what I did was (without thinking) stupidly rip my cord out of the wall while it was saving. I imidiately noticed I did this and powered-back up my PS2 to check the memory card, and all seemed well until I put the game disc back in and it said "No Data Has Been Found".
So there we go... I was replaying it back on Expert (luckily that mode gives you a ton of money so I could re-buy everything) and only got only to the guitart battle with Tom Morrello, life sometimes feels a bit rainy when it gets like this -_-.