The 200-400 is not as massive as I thought it would be, looks pretty hand holdable to me.Actually, the front element's diameter is much smaller than I had thought. I'm actually really surprised.
I wonder why neither of the photographers in the photo is using a lens hood.
Yup, 100mm diameter front element (theoretical), smaller than 300mm f/2.8 (107mm).
My guess in that there is a lens overall length restriction that prevent use of hoods with really big lenses. There is a 400mm f/2.8 at the top of the frame without a hood as well. All the other lens in the frame are 70-200mm with hoods (and one Nikon 200mm f/2 with hood). I've noticed in the coverage I've watched that the really big lenses (400mm f/2.8 +) do not have hoods.