That was my plan, along with using a distributed filesystem like glusterfs to replicate data across the network as backup. Unfortunately "time to go shopping" was ~1 month in on the second device (It was in a sub-optimal power situation...). A few hours, I had one machine with 7.5 TB of space and going on 4 months of uptime. ZFS has been historically BSD-only. Newer versions of the linux kernel are starting to support it, but I'm doubtful of the stability of a core module that hasn't undergone 10+ years of testing in the wild. It's got neat stuff to ensure data reliability on the drives, but if most people mount their storage over SMB (Windows shares) / AppleTalk, both of which negate the problem of ZFS support on OS X / Windows. Not sure about eSATA / USB...Whether or not you can dial into them when the host goes tits up I don't know; far as I'm concerned, if the host goes tits up it's time to go shopping anyway.
WTF is up with ZFS, by the way?
By the way, now that I'm back in town, I thought I would share...THE NETCLOSET: http://imgur.com/a/XihhA It's since gone through a number of changes, and is no longer quite so much a fire hazard. Sadly, the water pipes still remain.