USB 2.0 supports 5 Volt @ 200mA if i'm correct. it will be hard to fry anything on usb power. and also, it might be hard to (fully) power an fan (motor) as most of them draw AT LEAST 200 mA's. and i think if you really are afraid to fry anything, i gues you could even try to power the fan on 3.3V pin from arduino ?
the fan you linked to states this:
Current AMP: 0.22 (220mA)
so you will not be able to supply that by USB, though i do think it will spin..
and please check the arduino I/O pins max amp. if i recall correctly their maximums are around 40mA. so im afraid you must use transistors (thats a simple way) rated for 300-500 mA to power on or off the fan, and for the control, i don't know if PWM from arduino is able to control the fan, ill leave that to next poster because i don't know 