Indeed, I thought of responding when I read this, but I don't have a really good answer. I know there's a USB port on my NAS, but I'd always assumed it was for purposes of shutting it down safely in case a UPS kicked in, or to back up the NAS to another one. Neither of those mattered to me.
Copying files to the NAS is something I do via the LAN. Its very nature implies that a NAS is connected to a local network, and it's assumed that there are other devices on that network. I've frequently accessed the shares on my NAS, but always from one of the connected devices, never from its USB port.
