Defiantly true about it working with LCD's. Black background wouldn't affect the back light, and probably would take more power in straightening the crystals (hadn't thought of that)!
altyfc, I like your idea about speed of reading the page. A lot of people (especially people with dyslexia) can read better with a lightly coloured background, such as light yellow or green, rather than pure white.
(the pastel green background of The Environment Site is a great example!!)
Robin