Bandit,
I should have said rinsed, not washed (just water to get rid of most anything but the shell itself). As I recall, it is mainly to keep any animal mater out of the compost as it can attract pests and especially flies that carry unwanted bacteria and parasites. Numerous parasites and bacteria can kill off the beneficial life forms in the compost that break it down to the rich soil you want. To give you a more complete answer I would have to consult my wife's "Master Composter" course material...guess I should have paid more attention /forums/images/graemlins/frown.gif.