Backblaze looks like a great service, but like other cloud-based backup services, it does not store "your operating system, applications, and temporary files."
Out of curiosity, why is this? Are there copyright issues involved?
We don't store your operating system or apps primarily because without taking a complete disk image, you wouldn't be able to reinstall them typically anyway. Thus, it would take more of your bandwidth to get the files backed up, but you wouldn't be able to use them. (And you may get a false sense of security about them.) In general, our goal is to backup your data - the things you can't get back.
I cracked the screen of my iPhone 3G a few years back. Rather than get it replaced, I decided to keep it like that since the touchscreen was still perfectly functional. I thought it made an interesting juxtaposition, and I loved the looks of horror mixed with pity people would give it whenever I nonchalantly used it in front of them.