If you’ve never lost data, either by accident (say, a drive died) as the result of something you did, you will. It is only a matter of time. Effective backups are a must. Actually, several layers of backups. Kottke.org has a great little video about how Pixar almost deleted Toy Story 2 (via Dave Pell at Next Draft.) Watch it, it is only a couple minutes long. I’ve had some version of all of these happen, but never with so much at stake. Very scary.
Oren Jacob (who is in the video) fleshed out the story a bit at Quora, adding my favorite tidbit to the story:
And then, some months later, Pixar rewrote the film from almost the ground up, and we made ToyStory2 again. That rewritten film [not the one we had to recover] was the one you saw in theatres and that you can watch now on BluRay.