It is a very good idea, though it requires a bit more work. The "propeller" ; should be glued to the cork somehow, and the cork glued to the rotor (epoxy perhaps, or hot glue?). Otherwise it may come off and hurt the user. Also, the blades should be filed a bit, the edges trimmed, to make them less sharp... Otherwise, I like it :)
Ah yes, I believe it would be better to use an old mobile charger to power the motor, instead of risking damage to the USB port...