now this is something that might change backup architectures :
Zmanda, who resell Amanda based backup solutions are now offering offsite backups to Amazon S3.
Bandwidth and data security issues aside this offers a really interesting way of doing backup.
Backup has historically been expensive to do properly (tape libraries are not cheap) and offsite backups even more so - having sat in some surreal discussions of putting duplicate tape libraries in other people's (commercial) data centres it's very expensive to do, plus there are all the management issues that go with tape libraries.
S3 has resilience, is build on commodity hardware, and you pay for what you use. Now what you want to do is to build a joint facility like that by a consortium of universities and site it on AARNET, and suddenly we have some offsite backups for everybody who subscribes.
Easy. Backups are basically tar files no matter who's software you use, so if you use D2D2T locally you could keep multiple copies on the cloud host by doing some simple rsync scripts and delete rules. (poor man's hsm)