[dur-randir]

Believing in hints from Apple about software? Sweet summer child.

[khalic]

Still waiting for ZFS on OS X

[djxfade]

It was implemented in some of the earlier Leopard beta's iirc. Possible speculation from my side, but it was probably removed due to licensing once Oracle expressed interest in acquiring Sun Microsystems.

[BirAdam]

This mostly died because Apple's new security framework doesn't allow for unsigned kexts or writable root. This also killed most fuse implementations and therefore kneecapped stuff like SSHFS.