So the Jaguarboard is a very nice device, with lots of CPU power in very small size, which is great. However, it has neither USB 3.0 super-speed, nor gigabit ethernet. As such, it is extremely constrained in I/O bandwidth.
Let's say you want to use it as NAS. You can attach some USB 2.0 hard disk, but then the 100-base-tx ethernet is too slow for that.
Let's say you want to use it for interfacing a popular SDR board like USRP B2xx or BladeRF. However, the USB 2.0 is too slow for full sample rate/bandwidth. And even if the USB 2.0 was sufficient, again the Ethernet is what blocks the use case, as you will never get the data off board.
I can think of plenty of applications where some high-speed interface (with or without intermediate processing) between USB and Ethernet, but the Ethernet at 100 MBps is just too slow, even for USB 2.0 HS at 480 MBps.