Okay, I'll quit apologizing, just didn't want you to take it the wrong way. :frozen:
And despite popular belief, HDDs last much longer than optical storage media.
It's just that HDDs are often under constant stress for years, while optical discs just lie around.
Then HDDs don't last as long!

-.- I know what you're trying to say, but say it! Here, I'll say it for you, and if I make any technical mistakes then someone can correct me:
Submitted to the exact same stressors (e.g. time, temperature, and usage), magnetic disks are actually more durable than optical media. The dye inside an optical disc that you never use will eventually bleed out and/or the metals inside it will eventually migrate and cause permanent loss of data. The time it takes for that to happen is much less than the time it takes for data on a magnetic disk to naturally corrode, demagnetize, etc.
But as you pointed out, the biggest
practical issue is usage. Putting lab tests and technical specifications to the side, the fact is that we write to our hard drives often, even the ones we back data up on. (Consider that even if you have an ExtHDD and you only write to it once a year you still write to it many more times than you will ever write to a DVD+R or DVD-R:
once.) And the person with the raid setup?
He writes to his back-up drive as often as he writes to his main or "real" drive. Meaning that if his real drive dies on him one day 3-4 years after purchase, his back-up isn't far behind.
The reason for not using a server (as you suggest doing) is mainly to do with privacy and legal concerns. It is very expensive for a US citizen to find a server which will be willing to house legal doujin hentai, never mind digital copies of commercial hentai; and even if he could find that there's the issue of privacy, of knowing that the sysadmin can always snoop around his files (whether it's legal to or not).
Getting back to money, do you think you could find such a server and sign a contract
for under $20 a month? I doubt so. But that's what you'd need to do to financially compete with the alternatives: since a spindle of 50 good DVD+Rs can be had for about that price after one month and 2 good hard drives can be had for that price after 12 months (i.e. $240).
Most people I know who run big-scale hentai operations that
aren't through BitTorrent either:
- host it on their own servers (which is more expensive than ANY of our proposed means so far for backing up data! :XD: )
- run commercial enterprises and pay big bucks for big corporate servers