Drones have gone far beyond the battlefield. Filmmakers like Werner Herzog hire them for soaring aerial shots, farmers use them to scout fields, and hobbyists rent them just for fun.

The above video, obtained by The Washington Post, shows why that may not be the safest trend.

It shows a drone, filming aerial footage for a production company, plummeting into the crowd at the Great Bull Run in Virginia on Saturday. While nobody had to be taken to the hospital, four or five people were treated for minor injuries, according to the Post.

In fact, anyone can buy an octocopter like the one in the video for around $3,500. The machines have become especially popular with filmmakers, because it means they don't have to rent expensive cranes to shoot from above.

The rising popularity of drones, however, does raise questions about safety.

Small drones are regulated like radio-controlled airplanes, in that they aren't really subject to much regulation at all, beyond guidelines that say they should be kept under 400 feet and stay clear of populated areas.

While drones are technically banned from commercial use, the Federal Aviation Administration rarely punishes companies that use them. (After all, nobody stopped that production company from flying a drone over a crowd in Virginia.) Commercial farms are increasingly using them to monitor crops.

"We really would only pursue a civil penalty if someone was operating an unmanned aircraft in a reckless manner," FAA spokesman Les Dorr told Reuters.

Such was the case in 2010, when a group called Team BlackSheep was fined $10,000 after sharing dramatic video of a drone buzzing over the Brooklyn Bridge and the Statue of Liberty, which raised fears that drones could be used in terrorist attacks — or, at the very least, unintentionally crash into tourists.

In 2015, the FAA plans to open up U.S. commercial airspace to unmanned aerial vehicles. Then, the skies could be filled with drones recording street images for Google Maps, crowd shots, college football games, and more.

By 2020, the FAA expects 30,000 commercial drones to be flying over the United States, and that's not even counting the unregistered ones operated by hobbyists.

"I would guess there are already forty or fifty thousand aircraft in the hands of civilians capable of autonomous flight," Chris Anderson, former editor of Wired, told The Verge earlier this year. "That's far more than our best estimates of what the military has, and the number is going to grow rapidly over the next few years."