Most questions about USB something are about removable drives in general, and the fact that they happen to be connected over USB is just a matter of today's dominant technology. Maybe we should synonymize usb-drive to removable-drive.
We have a few questions about USB itself or about removable devices in general. I just went and retagged a few usb questions that were really about USB drives. That still leaves some questions about USB itself, justifying a separate tag.