That was actually the original inspiration for Snebu (not rsnapshot specifically, but a custom script implementing similar functionality based on the original rsync snapshot paper). Snapshots are so much better than level-based backups (full/differential/incremental) when using disk-backed storage.

I ended up running into this problem: https://news.ycombinator.com/item?id=8305283 when I got to 20 hosts and a year's worth of backups (14 daily, 6 weekly, and 12 monthly snapshots, so 32 snapshots per hosts). It was made worse in my case because I was using ZFS with compression. So the original implementation of Snebu used shell scripts, flat files for the catalog, and a small utility to burst apart tar files.