Everyone writes some kind of recursive backup tool, just like everybody writes their own templating system and TODO list manager. Set yourself apart.
I think it has potential. The problem space is complex enough that many different solutions can exist. For example, at my current job we ended up creating our own backup system that would let us easily sneakernet old copies of the data to our offsite location.
For what it's worth, some other open source backup tools that are similar are rdiff-backup and obnam. I've been meaning to make a page like http://en.wikipedia.org/wiki/Comparison_of_online_backup_ser... but for open source solutions.