Actually the incidence of Salmonella in raw eggs is quite rare (USDA has it at about 1 in every 30,000 eggs), and it is nearly impossible for it to penetrate the shell, particularly if the shell is not washed prior to packaging (washing removes a naturally occurring bacterial resistant protective coating, but is unfortunately mandated for non-farmer's market sold eggs).
Contamination occurs in factory farm settings when eggs come into contact with feces, and is transmitted when the shell is handled. Helpful tip if you're concerned about it: alcohol concentrations over about 27% kill salmonella, so if you're really concerned and want raw eggs, drop them into a vodka bath (40% alcohol) before using. No problems.