Are the two spheres mostly dark here because after one bounce the two spheres don't reflect light into our viewing point except for the two white illuminated spots?

I am actually curious about this as well. @kevinliu. I actually believe it might be because the light from the light source is the only light that is being reflected by the spheres. I think you're right, in that the one bounce only illuminated things directly. The two spheres get illuminated by the light source, but because of their behaviors they need the light to bounce off of the walls and ceilings to actually show any other types of illumination