When? All the damned time. Maybe you have an external HD or SSD based on USB, updating the firmware is perfectly acceptable. Same thing for HIDs and NICs. High

When? All the damned time. Maybe you have an external HD or SSD based on USB, updating the firmware is perfectly acceptable. Same thing for HIDs and NICs. High performance USB drives are basically little SSDs, and there's plenty of reasons for wanting to update the controller firmware on them to improve features or performance. It should not, however, be generally possible for arbitrary programs to update the firmware on a USB device without both the consent of the computer host's current user/administrator AND the device's manufacturer (subject to certain hedges and caviats of course). Right now many USB devices are just wide open, allowing this chaos of security vulnerabilities, that should not be.