I am continually astonished at people not backing up their stuff. Only today I was talking to a neighbour. His daughter has lost everything, probably because of a virus or some other kind of rogue file. Did she have a backup? Of course not.
At the risk of stating the obvious, it is really important to back up your work, and not just occasionally either. I know you do so, but here are a couple of cautionary tales you might like to pass on to your students or colleagues.
Cautionary tale #1: a few years ago a colleague's student lost all his work that he was supposed to send in to the Examination Board, to have marked. His teacher tried to appeal to the Board to give him the benefit of the doubt, but I knew what their answer would be, and I was right. Given that the course in question was a computer skills course, they said (quite reasonably in my opinion), that if he didn't even have the nous to take a backup of his work, he didn't deserve to pass. Well, they put it more diplomatically than that, but that was what they meant.
I would have asked his teacher why he didn't tell his students to take backups, but when I discovered, by chance, that he saved his own files with such descriptive names as Document1, Document2 and so on, I realised there was a deeper problem.
Cautionary tale #2: Having worked for -- I was going to say hours, but in fact it's days; and days; and days -- on two presentations for a conference in just over a week's time, I was dismayed when I switched on my computer this morning only to find that, overnight, the gremlins had got in and corrupted the disk. Not only could I not do any work on it, but I couldn't save any new work either.
I found that out because, being the paranoid type, I tend to save my work after each paragraph rather than at the end of the session. I even tried emailing the file to myself, but the email program was trashed too. It took the computer a total of five hours of chkdsking to sort itself out. That's the kind of stress I can do without.
Fortunately, however, being paranoid, I also back up my work every day to an external hard drive. I was therefore able to get on with it using my wife's laptop. And being even more paranoid than I am sure is healthy, I have now backed it up to the aforementioned laptop and two memory sticks. Later I shall back it up to the external hard drive and then tomorrow, just for good measure, I'll deposit a copy somewhere on the internet too.
Finally, just in case every single backup goes haywire, I've printed out my notes and the slides. I am not quite sure how holding up my printouts to an audience of (probably) several hundred people will pan out, but one thing's for sure: you can't say I didn't try! But seriously, I just figured that if the worst really did come to the worst, I could always scan my notes or simply memorise them, and use no slides at all. But I don't see that as being a likely scenario. Even I am not that pessimistic!