My eggs are very clean unless it has been raining, then they can be a bit muddy. Rarely do I have to wash them.
I am wondering if the cleanliness of the egg has to do with the kind/shape of nesting box? Are most people's boxes open on top? I would guess this would allow chickens to stand on the back and potentially poo inside the nesting box, or to roost for the night with their hiney hanging over the area where eggs are deposited.
For nesting boxes, I use a round cat litter box called a "Booda Dome". The opening is in the front, and the round shape keeps them off of the top of the box. Even if they were hanging out on top, they don't stay long because of the sloping shape.. not easy to hang out on.
http://www.petacular.com/products/Booda-Dome.html
and no, I did NOT pay $37 for mine, I paid $15.
My girls get in, deposit an egg and get out. I have to clean the boxes only every few months, as it just doesn't get dirty in there.
How are other's boxes shaped? I"m curious to hear if the engineering of the boxes show a pattern for dirty vs clean.