How about we all read this http://www.armscontrol.ru/UAV/UAV-report.pdf Threat of Terrorism Using Unmanned Aerial Vehicles: Technical Aspects By Eugene Miasnikov
This report has links to other report that will keep you busy reading for days.

Having spent several years in the RPV business as it was called then. I know just how hard it is to shoot down a 1/9th scale model of a Mig-27. On one ocasion I flew in front of 6 M-60's and 4 M-2's for days back and forth. They fired tens of thousands of rounds. Many of the planes would return clean after a 15 minute flight. If they decide to use a model for a weapon there is little to nothing we can do.