The FAA has released a list of all the organizations authorized to fly drones in the US, and while agencies like Customs and Border Protection and DARPA are on the list, so are several colleges, a dozen police and sheriff's offices, and the FBI. The release comes in response to a Freedom of Information Act lawsuit from the Electronic Frontier Foundation (EFF) filed on January 10th. While you don't need a license to fly something like the Parrot AR Drone, anything that flies at over 400 feet requires a Certificate of Authorization from the FAA. Currently there are about 300 active COAs, but the agency says it has issued between 600 and 750 since the program began in 2006.
As illuminating as the list is, it still leaves a lot of questions up in the air. For example, it doesn't specify which models of drones (or how many of them) each organization is flying. The idea of a constant eye in the sky is naturally contentious because of the numerous privacy implications — hopefully the FAA follows through on its plans to release more details so we can get some more informed opinions about future drone use legislation.