Until you suffer through your first bout of food poisoning it's hard to take food safety too seriously. I'd been warned about raw eggs my whole life but never heeded cautions against licking the bowl. Then I watched friends get sick with salmonella after tasting bad brownie batter. Raw fish didn't phase me until one fateful night when it did, leaving me bedridden for three days. And even though I started to take food safety a bit more seriously, I would still only think about it in the context of raw animal products. Then the news reports began: contaminated spinach, peanuts and tomatoes, causing people to eliminate these from their diets entirely. As though vegetables needed any more bad press.
I started to understand a bit better when, earlier in the spring, I was working on a project about broccoli sprouts for my Bioactive Compounds class and encountered all forms of warnings about the safety of eating sprouts. Why sprouts? Not because there's anything inherently unsafe about them - in fact, they pack an especially strong nutritional punch - the seeds, grains and legume have to be cared for when they are soaked, rinsed, sprouted for the couple of days it takes to grow them and they can become moldy. The real issue is seed contamination, so that if you have a reliable seed source and sprout your own seeds, and take the necessary precautions, there should be minimal risk.
Here's a link to the FDA's Center for Food Safety and Applied Nutrition's tips for food safety at the farmer's market.