Different standards...
We had usb, firewire and now we got e-sata. How about using ethernet with a reliable storage protocol as an interface. It has various speeds from 10 Mbit to 10 Gb while maintaining the same utp cable structure for some time now. It would even allow a storage device to be networked. For computer links like in the case of e-sata, we could use a simple disk controller chip, which can only provide single computer access and for large storage area networks, the controller could serve multiple machines based on it's space assignement maps. For security and speed, one could always use multiple network ports, so a local san unit could only be accessed from the computer that connects to it through an utp cross cable. It's an easy and cheap way. Adding standard serial ata/serial scsi over ethernet support to an external device would also be simple and then we could also get rid of the drivers, like in the case of the standard usb mass storage standard. Making a disk to have native ethernet ports would be even cheaper. All it needs is a network enabled controller chip instead of a sata/sscsi one. We could even use this layout inside the computer case too. This would decrease the number of data link formats from the current 11+ (pata,scsi,sata,sscsi,usb,firewire,pci,pcix,pcie,ethernet,dvi,spdif etc) to pcie (short range) and ethernet (long range, external). This is just a question of packet formats, because all new technolgies use the same physical signal format and can be carried through twisted pairs.