The US Dept. of Health and Human Services have tested the nation's ability to trace foods through the supply chain, and succeeded, 12.5% of the time. 

That's right.  87.5% of the foods they tested were untraceable, either part or all of the way through their supply-chain journey.  Witness last year's tomato salmonella scare, which, it turned out, had originated in Mexican hot peppers and not tomatoes. 

Why is nearly the entire US food supply untraceable, and therefore vulnerable to bacterial outbreaks or, God forbid, the T-word?  Mainly because the food industry likes it that way: 

AP: "In the past, the food industry successfully lobbied against efforts to impose electronic record keeping and other requirements that may improve tracing."

But apparently the tide is turning, and the Obama Administration and Democrats in Congress are promising to make food safety a priority.