Remember the good old days, when salmonella was something that was an issue with chicken or eggs? We've had recalls on spinach, tomatoes, cantelope, and now peanut butter.
Here's a good explanation of how these bacteria are ending up in plants. Once groundwater is contaminated with animal wastes, it can multiply inside produce. Washing the produce doesn't necessarily take care of the problem. Our food supply, which is more centralized and globalized, means that outbreaks that would have once been local now spread nationally and even internationally. The latest peanut butter case is so large because one plant in Georgia makes peanut and peanut butter products that are sold to more than 85 companies. Since one of these products is large containers of peanut butter for nursing homes and schools, people who are more susceptible to the illness are the ones exposed.
I am glad I make my own peanut butter, because I don't feel comforted by this answer to the question of whether it's safe to eat a peanut butter sandwich: "The FDA says as of Sunday there is no indication that brand name peanut butter sold in grocery stores is linked to the outbreak." I don't know what to do about the produce... it's too cold here for gardening right now.