Our Brian Fung brings word that Iran has a drone, and I think it's reasonable not to worry about it, per se.
But let's talk about the (very) near future.
Drones are not like the atomic bomb. There won't be a day when suddenly we realize that a horrible new weapon has changed the world forever. Instead, one day we'll wake up and there'll have been a terrorist attack by a swarm of drones launched by hand from a park across the Potomac from Washington, DC, and no one will know where they came from or who sent them. We'll wake up one day to a drone peering in our window as preparation for a common burglary.
The price of these unmanned aerial vehicles is plummeting from two sides. On the one hand, you've got the toys like the $70 iHelicopter you control with an iPhone. This little guy even has two plastic missiles you can fire!
There are already pretty good surveillance drones, too. Like this $300 Parrot AR.Drone.2.0, which can shoot HD video. You control it with an iPad. That quadcopter's users are already submitting video that looks like this:
And don't even get me started about these nanobot swarms.
At the other end of the spectrum, you've got the military-grade drones, which come with real missiles. These ones are still expensive and obviously procuring the bombs and missiles is still hard.
But the fancy, long-range drones have now left the Pentagon costing and production ecosystem. Hobbyists like Wired's Chris Anderson are working on high-capability DIY drones. Here's a chart showing the relationship between "drone/autopilot production volume and price."
The upshot of all this is that it's not going to take much to procure a drone and do anything you want with it. And if you try to outlaw them, then, well, only the outlaws (and government) will have drones.
To me, the best parallel is the improvised explosive device, the IED. This weapon gives every army/police force fits because the tech is cheap and commodity and its action is at a distance. What's going to stop anyone from turning a cheap drone into a flying IED? Or a swarm of cheap drones into flying IEDs? What's to stop your neighbor from hovering one above his house and streaming HD video of the neighborhood? (The current answer to that last question one is battery life on the toy UAVs, but that's improving, too.)
Semi-autonomous flying things are already available to the general public and will continue to become more available. Yet our intuitive privacy settings, our security forces, and our sense of property all assume humans on the ground.
Let me posit this: Drones will make traditional fences as obsolete as gunpowder and cannons made city walls.