There are a bunch of USB device classes with generic drivers that will work even with an unrecognized VID/PID. Mass Storage and HID (keyboard/mouse) are the mos

There are a bunch of USB device classes with generic drivers that will work even with an unrecognized VID/PID. Mass Storage and HID (keyboard/mouse) are the most common ones. I have only experimented a little, but it seems that unless your device requires a special driver, you can use the VID/PID of another device that doesn't require a special driver (e.g. some generic keyboards), there won't be any problems. There are probably horrible corner cases that I haven't encountered, though, so don't do this.