When Apple first hinted towards supporting Sun Microsystem's ZFS filesystem with the inclusion of a read-only driver in OSX 10.5 (Leopard), all the hardcore server admins and other extreme users listened with excited ears.
ZFS is such a big deal because it's a complete rethinking of how files are stored; rather than address them in blocks, they're instead placed into free space on the disk but older versions of the file are not overwritten in the process, meaning that the older copy will be available in case a write error occurs.
It also removes the need for RAID for mission-critical data and a host of other benefits, but with the removal of the ZFS read driver from OSX 10.6 (Snow Leopard) it's not very likely that Mac users will ever see this filesystem.
It's now speculated that Apple are working on their own competing filesystem, one that is supposedly advanced enough to compete with ZFS and definitely more modern than its now-aging HFS+ structure.
This means that the server and consumer world is going to have to wait awhile longer for ZFS or something inherently ZFS-like, and this also extends to Windows/Linux users.
Head to Arstechnica to read a little more about Apple's droppage of the storage tech.