The main reason I am asking this question is that the people who are pushing the use of the lens hood state that it prevents light from reaching your sensor, confusing the light meter on the camera. If this is so what about live view shooting? I would think this would be far worse in terms of light reaching the camera sensor. So if it is OK to shoot live view what is the big deal of using a lens hood?
The main benefit of a lens hood is that it keeps light from outside the image frame from impinging on the lens, scattering at surfaces, reflecting from surfaces (and potentially scattering off non-optical surfaces inside the lens body), and eventually (at low level) blanketing the frame in a way that reduces contrast.
The coatings on lens elements are also for this purpose, but no coating is 100% perfect; there is no case where light can pass from air to glass, glass to air, or even from one kind of glass to another, without some reflection and scatter. With modern zoom lenses sporting element counts from fifteen to twenty or more, there are a lot of surfaces that can scatter or reflect light -- and the less light that enters the lens that's not on a path that leads to the sensor (or film, as I learned this), the less gets scattered around and the better the contrast in the final image (prior to any processing, that is).