There is nothing wrong with using a toggle switch for a ceiling fan. You can even use a dimmer to control just the lights as long as the wattage of the lamps do not exceed the rating of the dimmer. The problem is when someone uses a dimmer to control the fan speed. They make fan speed controllers for this. On ceiling fans, you can switch the lights and fan separately with 2 wall switches. If this is something that you are wiring new, I would put the fans and lights on separate switches. And when I say that, I mean 1 switch for (6) lights and 1 switch for (6) fans