Guapo,
I think there is LESS here than it seems.
The actual backup, as groundzero3 says, is purely local to my network. So by one method or another, the backup app on my pc finds the drive on the local network and does its thing. The convenience this offers is being able to backup multiple pcs without having to carry a USB drive around to each one. (there's a speed/convenience trade off here clearly).
The other nice thing is that the drive has a connection to the wan so I can do a local copy to put stuff on it that you can access. Control of access is orchestrated thru the LaCie web which (apparently) keeps up with the ip address/port of the drive no matter what dhcp addess it has today. In addition, the LaCie site allows me access to the whole drive from anywhere which is a good thing.
So, as I understand it, a pure backup drive would be purely local thing. The remote access features are the value-add that needs the port forwarding & stuff.
(There is another level of stuff like music streaming to a player on my network that is still in the mostly-magic category, for me).
Tom