From The American Scientist:
As children, we played in the dirt, ate fruit without washing it, licked the juice from our grubby fingers and never fell sick, if memory serves. This last detail probably isn’t quite true, but it’s also possible that something has changed since we were kids—something in the food itself, or in society, that makes us more vulnerable than before. It certainly seems that we hear more frequent reports of people getting sick after eating fresh fruits and vegetables. Why is this? Is it just the press coverage?
Actually, no. It is indeed true that, for fresh produce, the number of outbreaks of food poisoning caused by microorganisms has risen in recent years. There are many potential explanations for this trend. Perhaps most significantly, people are eating more fresh fruits, vegetables and salads than ever before, and more meals are eaten outside the home at restaurants or public gatherings—the most common settings for contracting foodborne illnesses. The greater risk stems partly from centralized preparation and distribution, which can spread contamination over a large volume of food, and partly from the greater number of people in contact with the food—meaning more chances for poor handling and storage.
More here.