This is such an interesting discussion! As chickenannie says, we humans harbor fantastic numbers of bacteria on our surfaces and in our guts. They outnumber our own body cells by about 10 to 1, and are actually essential for our health and survival (they make vitamins we can't, for example). Nonetheless, the bacteria that inhabit chickens are not necessarily the same ones that inhabit humans, so it makes sense to think about this topic. I read one report that says an unwashed egg typically has about 30,000 bacteria on its surface.
I also read that about 30% of commercially-produced eggs have poo on them (!!!). In the U.S., commercial eggs are washed in hot water containing a high pH detergent that gets rid of the poo and most external bacteria. Washing also removes the cuticle that protects the eggs from being penetrated by any remaining bacteria. Scrupulous refrigeration keeps bacteria that do enter the egg from multiplying quickly.
So, the inside of an unbroken egg you buy at the store should be mostly sterileunless the chicken that laid it was sick. A chicken infected with Salmonella enteridis or another bad bug will pass the bacteria right into her eggs, and if those eggs aren't cooked completely, whoever eats them will be exposed to the live bacteria. This is a problem with battery layers because they live overcrowded, unnatural living conditions. Those of us who raise chickens in a more natural environment don't need to worry so much about Salmonella because our birds are naturally healthy: Their immune systems are intact, so they are less likely to get sick with a bacterial infection.
Personally, I like to keep our nest boxes spankin' clean so there is no poo on our eggs to begin withremoves the grossout factor from the equation. But even our clean-looking eggs undoubtedly have bacteria on their surface because of, well, where they come from. Nonetheless, I'm with the folks who wash eggs just before eating or not at all. I wash our chickens' eggs only when I'm going to boil them. If I crack them raw, I do it carefully so the egg white or yolk doesn't touch the exterior of the shell. And then I wash my hands. I'm just not worried about the few bacteria that get past my sterile technique. Honestly, I'm more worried about eating eggs from a commercial operation, where Salmonella may be rampant.