Now that I've thought about it, I think I know why some people seldom have problems with any HDDs but the worst, while other people struggle to find drives that last. The ideas can apply to other components as well, but I chose HDDs as being probably the most hotly debated component in the PC (with the possible exception of SSDs) when reliability is the subject of the matter.
It's about resilience — how well the drives cope with less-than-ideal treatment; heat and shock being probably the main influences here. One of the critical distinctions between enterprises and desktop users (I hate using the term “consumer-grade” as it simply doesn't make sense from a resources standpoint) is that while enterprises tend to be very careful about drive handling and cooling, desktop users…not so much. If nothing else, the average user doesn't expect to have to operate their PC in an air-conditioned room at all times.
So my current assertion is that while the factory defect rates are not especially dissimilar (barring the truly dreadful drives), the resilience of the designs does vary quite a bit. This would explain why the Seagate Barracuda ATA III/IV/V and 7200.7 were generally considered to be more reliable than most HDDs — not that they're indestructible, but that an ST380011A I had lasted for the equivalent of 4.5 continuous years even with inadequate cooling (the highest recorded temperature was 67°C!) for the first 3 years of usage (the specification being for 5 years) says something for them.
