The use of unmanned aerial vehicles (UAVs) inside US borders is relatively new, but some might be surprised at exactly how many of these devices were currently active.

As of Dec. 1, the Federal Aviation Administration (FAA) had reported over 270 active authorizations for the use of drone technology in the US -- with the largest permit holder being the Department of Defense.

NASA had 11 percent and the Department of Homeland Security maintained 5 percent to monitor the borders, according to The Washington Post.

The FBI and law enforcement represented a minority of authorizations, but their share was quickly growing.

Soldiers returning from war have created a new breed of law enforcement who are used to having aerial surveillance in their arsenal, experts at New Mexico State University and Auburn University told USA today.

Local governments were pushing the FAA to propose new regulations that would allow for even more UAVs in the skies. Those new rules, expected to be in place by 2013, would allow unarmed drones to fly up to 400 feet above the ground.

"Not since the Taser has a technology promised so much for law enforcement," Ben Miller, a spokesman for the Sheriff's Office in Mesa County, Colorado, told the Post

Cost alone make UAVs attractive to local law enforcement. A drone can cost less than $50,000, while a new helicopter can run more than $1 million.

A drone called a Draganflyer had already been used by Miller's office to search for missing persons.

The Texas Department of Public Safety had also recently obtained an emergency FAA authorization to use a device called a Wasp to spy on a suspected drug dealer.

The Wasp weighed less than a pound, and could be equipped with electro optical (EO) and infrared (IR) cameras. Originally designed for use in war zones, the device was silent and nearly invisible in the sky.

"But when drones come to perch in numbers over American communities, they will drive fresh debates about the boundaries of privacy," the Post noted. "The sheer power of some of the cameras that can be mounted on them is likely to bring fresh search-and-seizure cases before the courts, and concern about the technology's potential misuse could unsettle the public."

"Drones raise the prospect of much more pervasive surveillance," American Civil Liberties Union's Jay Stanley told the paper. "They can be a valuable tool in certain kinds of operations. But what we don't want to see is their pervasive use to watch over the American people."