When video of the brutal assault of a transgendered woman at a McDonald’s near Baltimore went viral last week, McDonald’s released a statement: “There’s no room for violence under the Golden Arches.” But in the annals of American crime, the fast-food-chain assault has become as iconic as the postal-worker shooting spree.

In January, Toledo, Ohio, resident Melodi Dushane punched out a McDonald’s drive-through window when she was told they didn’t sell Chicken McNuggets in the morning. Another woman recently drove through a crowd of people in a McDonald’s parking lot, injuring four. In 2008, a Los Angeles man punched a 16-year-old girl in the face at a McDonald’s after she complained about him cutting the line. A Wendy’s customer reportedly assaulted a female clerk at a drive-through window in 2007 after she didn’t tell him to “have a nice day.” The list goes on. Spike Jonze even made a fast-food beating the centerpiece of his music video for Arcade Fire’s “The Suburbs.” (You can find a compilation of restaurant violence here.)

Fast-food restaurants haven’t entirely replaced banks as crime targets, and criminal activity in such places is no longer on the rise. (Crimes like this, however, are.) The Bureau of Labor Statistics estimates that the number of homicides at “limited service restaurants,” which include fast-food chains like McDonald’s and KFC, has declined from 35 in 2007 to 15 in 2009. But fast-food establishments like Wendy’s and Burger King do see more crime than their “full-service” counterparts, like Ruby Tuesday’s or the Olive Garden. BLS estimates that the rate of assaults at limited-service restaurants is more than twice as high as at full-service restaurants. Whereas sit-down restaurants had 0.8 assaults per 10,000 employees in 2009, fast-food joints had 1.8.

Why the difference? The primary reason is that fast-food chains are unusually vulnerable to robbery, which accounts for most of the violence at fast-food stores. Like gas stations and convenience stores, fast-food chains open early and close late. But customers there tend to use cash more than at gas stations, which have switched almost entirely to credit cards. And unlike convenience stores, fast-food places don’t always limit the amount of cash that an employee can access. It doesn’t help that fast-food workers are paid so little. More often than not, the robber is a friend of an employee or an employee himself. Location is a factor, too. What makes McDonald’s restaurants so convenient to customers—they’re located at major thoroughfares and intersections—also makes them great robbery targets. (Drive-throughs make for especially easy getaways.)

Demographics play a role as well. McDonald’s bourgie makeover notwithstanding, most fast-food chains cater largely to young, low-income customers. (Burger King’s since-abandoned “The King” campaign was specifically aimed at “young adult male consumers.”) Restaurants in high-crime areas will occasionally become crime scenes. Fast-food chains become easy places to loiter, which can lead to arguments or worse. “When you’ve got a relatively uneducated, young workforce and piss-poor management, put them in a high-stress situation—a burger-and-fries environment—and you’ll get some improper conduct,” says David Van Fleet, a professor of management at Arizona State University and co-author of The Violence Volcano: Reducing the Threat of Workplace Violence.

Customers may feel stressed out, too. Professors at the University of Toronto released a study in 2010 concluding that exposure to the logos of fast-food chains like Wendy’s and Burger King made people hasty and impatient. When “fast” food doesn’t live up to its name, people might lash out.

The “trend” of fast-food violence isn’t really a trend. Any apparent uptick in domestic abuse at the Home of the Whopper probably owes more to YouTube and camera phones than to growing unruliness. But as with postal workers, all it takes are a few bad apples. Goodbye “going postal”; hello “McRage.”