Drobo is "cool" but my question is why only DAS (direct attached storage) and not NAS (network attached storaage) as well?

For me, I like to backup across the network so I have an ethernet HDD connected to my router. All my Macs/PCs can offload to there. Granted it's more of a fileshare than a backup, but a singlepoint backup works for me. Being able to swap drives there would be fantastic, and making it worry free would be golden if it was Drobo.