I believe there is a proof of concept evil USB device that looks like a USB key, but actually emulates a keyboard and enters all sorts of damaging keystrokes when plugged in. So allowing keyboards is dangerous anyway (although having the screen locked should help).
This is the reason why keyboard/mouse connectors should look different to USB connectors, so we can tell the difference.
This is the reason why keyboard/mouse connectors should look different to USB connectors, so we can tell the difference.