I can't think of another product category less served by the ol' "world's smallest" tag that gadget-makers continuously foam over than network storage drives. But, of course, here we have the "world's smallest" NAS.
The miniNAS, as you would expect, uses a pair of 2.5-inch laptop drives (up to 500GB each), which are wrong for a NAS for a number of reasons, primarily their lack of speed when compared to 3.5-inchers. At least your data will be backed up, with both RAID 0 and RAID 1 as an option.
Also packed in is a DLNA server for iTunes and multimedia streaming, a USB port for backing up USB volumes, and, in the only benefit of the laptop drives I can see, a claim of 25-30% of the power usage of a full-size dual-disk NAS.