I know it could but I really don't want to be told every time!
I've unset the "Tell me if this device could perform faster" option in Device Manager / USB Controller / Advanced dialog box. Makes no difference. I've set the USB 3 monitor in Notification Area Icons to "Hide icon and notifications", but still it pops up.
Is there any way of actually stopping it happening? Perhaps by inhibiting this USB 3 monitor - if I could find out how to.