I am not sure its too much a problem here in the UK yet, but one area I see these drones being used and abused is by the Press..

There are laws that supposedly prevent them being flown near people or private property, but with todays cameras and zoom lens, that's not going to provide much protection from snooping..

The other area of concern is there use by terrorists. Even moderately low end models have GPS guidance, which means low cost off-the-shelf auto-pilot technology is now easily within their grasp..

While many consumer grade drones have very limited payload/range, I predict that the auto-pilot technology alone will end being used in other terrorist related applications..