Who is it for? For everyone in the whole world!
Where will it be used? On the Internet!
There are several alternatives for backup, of which most is software solutions that lets you take responsibility that the backup is stored in a safe place. A safe place would of course be another geographic place, preferably several since certain types of disasters can hit against big areas.
Some companies offer storage space on the net, small volumes is free of charge but larger quantities (gigabytes) costs money. The cost is however sky high in proportion to how cheap storage is.
A P2P system for backup. The concept is that you choose which data that will be back upped and share space on your own hard drive for others to put their backups on. The great thing about P2P is that you can spread out the backup on many computers, and if you are the paranoid type you could let many copies of the data exist, just in case some peer happens to be offline. The amount of data you can have backup on is of course proportional to the amount you let other use on your own computer for their backup, if you share 100GB you can have 5 x 20GB back upped data on the other computers in the system. The good thing is that you can decide how safe you want to be.
The cost is low since storage is so cheap. The only actual limits are your connection to the internet, since with a slow connection it can take considerable time to do a full backup.
The data is of course both encrypted and divided in small blocks and spread out through the P2P-network. This means that you safely can place your data on other people's computers.
The system is centralized with a hub, which distributes the resources among a private party of connected users.