Zaurus writes "Apple has replaced its ZFS project page with a notice that 'The ZFS project has been discontinued. The mailing list and repository will also be removed shortly.' Apple originally touted ZFS as a feature that would be available in Snow Leopard Server. A few months before release, all mention of ZFS was removed from the Apple web site and literature, and ZFS was notably absent from Snow Leopard Server at launch. Despite repeated attempts to get clarification about their plans from ZFS, Apple has not made any official statement regarding the matter. A zfs-macos Google group has been set up for members of Apple's zfs-discuss mailing list to migrate to, as many people had started using the unfinished ZFS port already. The call is out for developers who can continue the forked project."
Daring Fireball suggests that Apple's decision could have been motivated by NetApp's patent lawsuit over ZFS.