This past July, my other computer effectively crapped out on me thanks to a program that I'd run several times before without any incidents. This past week, a flash drive that I'd been using for a while broke becuase it was yanked rather forcibly from the computer I'm using right now.
Both cases resulted in CATASTROPHIC data loss.
While the flash drive case wasn't as problematic as the computer crash this past July, the flash drive featured data related to SCPs I was going to post…none of which I had bothered to back up on any other flash drive or computer. As a result, I lost three SCPs-in-progress, several documents related to the Order of Belphegor and a major chunk of other important info.
Moral of the story, kids: ALWAYS back up your data. Never rely on just one flash drive or just one computer or just one set of CDs, because that one flash drive can break, and that one computer can crash, and those CDs can get completely and utterly wrecked.