i would still be leery of driving any motor off of a port, they are not generally made for decent amperage, and putting your finger on a decent fan can draw double digit amps, yea that is a extreme worst case, but when connecting it to a port made to deal with at best a few hundred miliamps...

edit: plus the electrical noise, and reverse emf, and becoming an ac generator when spinning down and ... just use drive power (imo)