ATLANTA

URBAN food trends, as delicious as they are, can have a dark side.

Backyard chickens offer fresh eggs and give the citybound a way to touch the country. But with them can come all manner of tricky diseases and noisy roosters.

An edible schoolyard is a terrific idea, until budget cuts and waning volunteer interest turn the plot into a tangle of weeds, forcing someone to explain to second graders why their beloved tomato plants died.

Now comes the modern food truck, where innovative cooks on a budget drive their kitchens around searching for what appears to be an endless supply of diners with Twitter accounts willing to line up for Korean tacos and salted caramel cupcakes.

What could be wrong with that? For some, plenty. From Los Angeles to New York, and Portland, Ore., to Atlanta, cities are wrestling with a trend now writ large on their streets, trying to balance the cultural good that comes with a restaurant on wheels against all the bad.