depends...
If you never get the post wet, it probably makes no difference. If you ride in the rain and/or wash your bike, allowing water to enter the seat tube, then a little light lubrication might be wise. If unlubed, at least remove the post and dry both the post and seatube after exposure to water.
I've never lubed a CF or Al post in any of my CF frames, but I never get them wet.
