Photographs aside, everything important I've ever written or stored would fit onto a smallish memory stick.
I also upgrade on a relatively frequent basis, so I have less concern about a hard drive than I do with the operating system throwing an bigger spanner in the works than a few letters changed in a word document.
For those more concerned, perhaps a server grade processor with associated motherboard using ECC memory would be a start.
Keeping all data on a very redundant RAID array should find flipped bits and correct them as a normal part of its function. It's quite interesting seeing how many drives you might need. Wikipedia has a decent explanation but three drives is a good starting point.
You'll also need a UPS in case the power goes mid write.
Personally, I think half of the problems are software and the other half from shonky builds using sub-standard components (especially the power supply) or just old equipment. Add in dust build up and some machines (mainly laptops) designed to make cleaning the cooling system a task for an expert and you're just asking for trouble.
As a final point, even with a full sized PC, the cooling solutions are usually so poorly designed they are asking for trouble. The venerable PC case was designed for components that drew a few 10s of watts, not the space heater components that you can buy these days. Some of the Intel chips draw 250W under full load and Nvidia's (about to be be released) top end graphics card need 3x8pin power connectors to supply the 350W of power that it requires.
Many are using water cooling in an attempt to move all of that heat and most of these folk seem to forget that watercooling systems tend to gunk up over time and if they don't keep the rest of the motherboard cool they will just run in to problems by cooking the memory and hard drives.