for sure these are a potential aviation hazard but let's put that into perspective; We've had tens of thousands of RC aircraft flying around, some of them quite large, for the last three or four decades with very few safety incidents.
ShotOne, Good point, and that's just radio controlled models. In the late '40s and early '50s when aeromodelling was at its peak, there were estimated to be two million model fliers.* It wasn't unusual for models to be found 20 or 30 miles from their point of launch if the dethermaliser failed. Allegedly, at some RAF stations, just about everyone from the Station Commander down went out on the airfield at lunchtime with a model and a can of diesel fuel.
Bearing in mind that these models had no external guidance at all, and you wouldn't want your jet engine to ingest a wayward Mills 75 or an ED Comp Special, how much of an outcry was there then?
*
http://www.flightglobal.com/pdfarchive/view/1947/1947%20-%200477.html