Plugging fans inito a USB port
You can draw maximum 500mA from a USB port, so 3 x 120mA should be OK. BUT the rated current is for 12V, you'll have to check what it is at 5V. Apparently at 5V the current should be lower as well (thanks, JGord), so this should work.  

If you overload the port's power supply it should cut off the power.