It isn't that new ... back as far as 1939, the German Air Ministry had proposals for remote-controlled planes carrying a tonne of payload for 300 miles. The remote control aspect wasn't reliable enough, so it was replaced with a basic autopilot to become the V1 "flying bomb". (Even in WW1, there were projects afoot; in WW2, the US Army alone bought 15,000 drones.)

The significance of the Iran incident is not so much the loss of the drone itself, but that the Iranians were able to capture it, indicating considerable control. Merely jamming the control signal should have been difficult - getting enough influence to land it somewhere is worrying.

IAN: "I think there is more chance that terrorists will get to realise their potential against the soldiers on front lines."

Technically, that use of unmanned aircraft is almost two centuries old now! The Austrians used balloons carrying explosives against Venice, with limited success, in 1849. Against front-line troops, I doubt it would work well - after all, you can use simpler weapons: grenades, mortars, RPGs - but against civilian targets it could be quite effective. Fly a radio controlled plane into a Superbowl crowd, for example: a small enough explosive charge to be carried wouldn't achieve much, nerve gas is hard to find - but a few pounds of simple pepper spray would cause panic and chaos with people thinking it was some sort of deadly chemical. Remember, there were 96 fatalities and 766 injuries in the Hillsborough disaster in England; imagine a crowd of 100,000 trying to flee a terrorist chemical attack.

The TV series NCIS actually featured a slightly less ambitious drone attack by a Hamas terrorist cell, aimed at the crowd awaiting a returning US aircraft carrier, thwarted by the NCIS team physically capturing the control unit for the drone before the attack was carried out.

A purely remote-controlled drone, like current ones, isn't that interesting legally or philosophically: it's still an aircraft operated by a pilot, even if the pilot's at a safe distance thanks to technology. If a US pilot fires a missile at something he shouldn't have, why does it matter whether he was six feet or six timezones from the missile when he fired it? (Or indeed from a submarine weapons officer firing a Tomahawk from 600 miles.) It's different psychologically, of course, because of that safety aspect, but it isn't until you have aircraft able to fire weapons autonomously that culpability becomes an interesting problem.