There are reasons why most weight-saving strategies start with the wheels and cranks-- beyond the obvious fact that a lot of weight is carried in those components.

This is an age-old discussion, and I can't get mired in some sort of physics lecture at the moment, but if rotational versus static weight didn't include some key differences, we wouldn't have these discussions to begin with. Let it suffice to say that there are forces at work that keep the Earth spinning, but it's also important to note that bike wheels and planets have as many differences as they do features in-common.