[problems]

It's tried and true tech that any competent ops person can use quite easily. Been around much longer than EBS quite frankly.

Dropbox targets end users who don't have the knowledge required to use the alternative, if you're smart enough to use EBS you're probably smart enough to use ZFS snapshotting just as easily. Or could within a day or two. It's really not that hard.

Like I said, there are systems that pretty much manage the whole thing for you and just warn you when something is about to blow up like FreeNAS.