I agree with those who are tapping #14 onto #12 for lighting circuits. From a very practical point, if you are running a wire to one light fixture, you can be assured that the load will not exceed the wattage of the light bulb. So we are talking about 100 or 150 watts. Where is the harm? #14 on a 15 amp breaker should be fine for receptacles as well. I wouldn't run to a receptacle from a #12 - 20 amp circuit and tap a #14 to it, though, because the receptacle could see more than 15 amps connected load.
