Like you originally stated, "empty" is somewhat misleading because there are energy fields in the vast "empty" areas, & in that way it can be stated loosely that inner space is akin to the vacuum of outer space.
Thing is, those electrons are moving so fast that they are almost in many places at once. I would imagine that a diamond has a whole lot of electrons whipping around constantly.
this story I read the other day was interesting
Their Deepest, Darkest Discovery
Scientists Create a Black That Erases Virtually All Light
http://www.washingtonpost.com/wp-dyn...nation/science