I think I remember hearing this called the "Dracula effect" or something similar. It's all the electricity being used by 24/7 plugged-in digital clocks, electric toothbrushes, cells/PDAs being charged, TVs, anything with a lighted display, etc.. Small stuff at one level, but is a large drain cumulatively.
It's lost as heat in the winding of the "wall wart" & internal transformers on gadgets that are plugged in...