Digital data is vulnerable to all kinds threats, from hardware failure to fire and theft. Do you keep regular backups of everything? You do? Excellent! Where are they?
I know of at least one person who stored their backup tapes next to their computer, and had both stolen together. The moral is to keep an offsite backup of everything that matters. Applications like Dropbox and Windows Skydrive make this easy to do, and unless your files are really huge, these solutions are relatively cheap. There's really no excuse not to use them.
Over the last couple of years, though, there has been an increasing move towards