By spending effort and providing tools for data recovery and file system repair (since btrfs is neither stable nor mature these leave much to be desired but the effort is clear and it is quite a contrast compared to ZFS).

The ZFS stand on this is that nothing can go wrong. If something does go wrong, which by the way is impossible, you better have your backups ready because you are on your own.

A good fact to keep in mind is that ZFS is meant to run on adequate hardware. ECC Ram (ZFS is more prone to corruption from random memory errors than most other filesystems, it assumes your ram is reliable), drives that don't lie about writes, adequate CPU overhead. it was designed to go BIG - and when you go big, these things are a given. If you skimp on any of these, it doesn't look as good - but small-scale wasn't it's target market. (And I'm not saying nobody should use ZFS on a small scale... but it was designed with some specific assumptions that are perfectly fair given it's target market)

If you are runninga a system at a scale where ZFS makes sense and not making backups of critical data, your operations process is fundamentally broken anyway. ZFS doesn't change the need for backups one bit (and it brings to the table some novel ways of doing offsite snapshots and whatnot, to boot)