Hope this isn't too stupid of a question...

Is there any reason that a polarizer should not be used in place of a neutral density filter? Of course, the polarizer will have an effect on skies and reflections. But I suppose I am asking, if you're shooting a scene where a polarizer doesn't have any effect, is there any reason not to be lazy and leave it on the camera (assuming you used it previously) rather than replace it with a ND filter?

So far as I know it is fine. At least I haven't noticed any issues.

A polariser also warms up the colors a little bit, so there might be a little difference. I use it all the time when I need low shutter speeds and adding a ND filter is not enough.

I agree with Bart

If you "dial in" the polarizer 90 degrees to the sun and then shoot into the sun it does not just act as a ND as Bart says. I do it all the time.....lazy buggar I am

Keith