Controlling the rate and location of snapshots, mostly. I've broken out some kinds of datasets (video archives) but not others historically (music). It doesn't matter that much, but I want to split some more chunks out.
Fair enough. I've personally slowly moved to a smaller number of filesystems, but if you're actually handling snapshots differently per-area then it makes sense (indeed, one of the reasons I'm consolidating is the realization that personally I'm almost never going to snapshot/restore things separately).
