I'm not exactly sure how many reptiles began carrying salmonella, but I do know it's considered more prevalent in aquatic turtles and green iguanas than in snakes. That said, I believe I read on one of the forums that any reptile can carry the salmonella bacteria...but you're much more likely to find it in raw meats purchased for human consumption, especially poultry and poultry products. Chicken and eggs seem to naturally have the salmonella bacteria and that's one of the reasons it's so important to eat both of these foods well cooked and to clean & disinfect all surfaces the raw product has come in contact with. That said, there are still countless people across the world who fix raw chicken on the counter and use a wet paper towel or sponge to wipe up the liquids, or who eat eggs sunny side up & runny, raw eggs, or lick the spoon after mixing cake batter. They are far more likely to come down with a case of salmonella poisoning than the average herp keeper. However, you can be if one of those people owns a reptile, it's that creature that will get the blame and not the dead chicken carcass lying on the countertop.
For prevention, it's important to wash your hands after handling your reptile and to NOT clean their water bowls in with your dishes. It's probably overkill, but I clean all my reptile bowls in the spare bathroom (the sink for small bowls, the tub for large water tubs that don't fit in the sink) and then disinfect the sink and/or tub with a mild bleach & water solution afterwards. I don't put my snakes on my bed, kitchen table or countertops, but they go just about everywhere else. I use old cotton sheets for substrate and those are washed in my clothes washer in hot water with plenty of soap & a good amount of bleach. A good way to keep the bacteria down, salmonella or otherwise, is to practice good husbandry and keep the cage clean & the water bowl fresh...and no frenching your snake. LOL
Raven