This piece from The City Fix looks at the trend in Washington D.C., and how the city's government is reacting.
"Planners are thrilled at the food cart craze too, as carts can enliven the urban environment and revive dead spaces, such as parking lots. In times of recession, street food seems even more important, providing affordable eating options to citizens and allowing culinary entrepreneurs to open businesses with lower start-up costs.
However, this trend has developed in spite of the challenges facing mobile food vendors. Food carts don't seem to fit into cities' normal regulatory structures – they're mobile and can cross jurisdictional lines, but they also need to park, and are often not welcome in public or private spaces. They sell food and need to pass health inspections, but they're not traditional brick-and-mortar restaurants. They offer a service to customers but not necessarily amenities like restrooms."