[Sarki]

That's the reason why there was a USB port on each side of the original Apple keyboard (not the wireless one of course). These ports (on the back) are most likely located there with the idea of having a device pluggued in for good and not moved so often.

[johnchristopher]

If memory serves me well those keyboard USB ports weren't amped enough to handle power hungry devices though.

[musicale]

They were primarily for connecting a wired Apple mouse on the appropriate side for a left or right-handed user.