[jbronn]

While it's true you can't expand a vdev, you can always add another vdev to a pool at any redundancy level you desire to expand capacity. For example, you could add a trio of drives as a raidz vdev to a pool with an existing mirror vdev (`zpool add mypool raidz dev1 dev2 dev3`). However, the drawback is that the expanded pool won't be "balanced" unless its datasets are rewritten.

[tscs37]

Home users would rather just add a single drive instead of having to worry about adding entire RAID setups.

[alyandon]

Exactly that. I can essentially add/remove drives on a whim (for any reasonable definition of "on a whim") using btrfs and run a rebalance command afterward and I'm done.

That, of course, is really not a concern for enterprise use cases.