Well, hard disks, fans and CD drives are pretty much the only moving parts in your modern laptop - and moving parts are what suck the most juice. To help make the battery life last longer, the components used in mobile devices actually have their power shut completely off. That's all I was talking about.
I'm sorry if it sounded like I was "talking down" to you. I wasn't really intending too. As for your points on commodity hardware - you are precisely correct. It's not a question of *if* a HD will fail - it's a question of whether the OS will crap out first.
For this reason, all the desktop machines I have use mirrored hard drives and either Linux or MacOS. That's about the only way I can get a good 5-10 years out of a box without having to waste my time re-installing the OS (and apps, etc).