The Raspberry Pi is a fantastic device for all kinds of things, but there's no denying that it can be clunky and unreliable. Sometimes, for no apparent reason, your Pi will fail to boot, which is why MakeUseOf suggests cloning your SD cards right after you get them set up.
Cloning your SD card is really simple. On Windows, you can use Win32DiskImager, and on Mac you can clone your card from the command line. So, once you set up your Raspberry Pi with all your XBMC plug-ins or all your retro games, clone that SD card so you'll have a backup ready if anything goes wrong. Head over to MakeUseOf for a guide to backing up and restoring those SD card images.