I pulled an old backup hard-drive from a safe to look at some old pictures. There are entire date folders that are empty. I'm not too worried at this point as they were also on the laptop, DVD and another backup hard-drive. Anyone putting all their faith in an electronic device with a 5 yr warranty is deluding themselves with the convenience. You will lose everything, it is a matter of a few years.
Bit rot (aka data evaporation) is a danger with all digital media, whether magnetic, optical or flash-based. The reasons differ with each form of storage media but the consequences are still the same. A quick primer:http://en.wikipedia.org/wiki/Bit_rot
Having said that, physical media such as film and prints also need their own set of optimal conditions to be suitably archived. As an example, merely storing these in dark conditions may not avoid fading since some dyes are prone to dark-fading.
Then there are the constant dangers of humidity, heat, vermin, theft, fire etc., which pose a danger to all forms of media.
I still stand by my prior post recommending prints as the preferred long-term archival medium (suitably printed and stored, of course, and ideally in combination with other archival strategies/media). Edit ruthlessly and print only your strongest images, and you not only have your archive but also a coherent summary of your life's work ready to be viewed without the need for intermediary technology such as a lightbox, enlarger, slide projector, monitor, computer, scanner, printer etc.