Quick App Idea
Here's an idea for a distributed, peer-to-peer (though not massively distributed, probably no more than three nodes in any network) backup system that's sort of a mix between Dropbox and a backup service like Carbonite or Backblaze.
Off-site backup is probably a really good idea. But. I'm not sure if it's a good enough idea that I want to pay a monthly fee for it. And I would imagine that most people have a significant amount of excess storage in their homes. So this app would incorporate that excess storage with the background syncing of one of the services mentioned above.
Here's how it would look in practice: you and a friend install the software and set aside a certain amount of space for the other user. You set certain folders to backup, and the software waits until it's late at night or cpu/bandwidth is not being used, and syncs the folders to an encrypted thing on the other node.
It would be fairly fire-and-forget, though it would have to notify you if you're getting close to the storage limit you've been allocated by your friend (stingy jerk).
You could also just set this up between your home and work computers, say. I can imagine, too, for even more simplicity, a completely closed-box system, a piece of hardware that's basically a big hdd with an ethernet port and this app on it that you could stick on a friend's home network or your work network.
I'd pay (once) for this.