And that $100 would only get you 20GB, so you'd be limited to a total of around 2.5 of those 1080p movies you're apparently throwing around (assuming a conservative 8GB each). And it'd take approximately a million years to sync them on any typical home broadband connection. And you'd better not be doing that over 3G, oh boy.
No, moving to THE CLOUD just gives you a different set of problems.
It's no surprise that people don't understand its utility. Quite honestly, it seems like most companies don't implement backups particularly effectively. If "professionals" can't get it right, how does giving someone a filesystem solve the problem?
My suggestion to you is to think about how a post-PC device should solve the disaster-recovery problem in a way that appeals to postPC users. If you can invent something that a luddite like me would use, you have a YCombinator startup right there.
Think about DropBox as an example. It's a folder. And it syncs. DropBox is right on the edge of PC/Post-PC. It still works with files, but all of the moving parts are out of sight.
So go out and invent the post-PC disaster-recovery mechanism. Make it like DropBox, not like backing up music. Just don't try to drag people backwards to being sysadmins. That's not going to work.
You plug your device in, it synchs, and then you're free to fling it out the window. No monthly fees to keep up with, and if done well, it's basically a one-time $100 back-up investment. Make it work easily with OS X and Windows, and people like my parents would never have to worry about the dog eating their laptop again.