There are risks connected to possible impact or improper over-flight of critical infrastructures (critical because of the potential safety risks or because of political sensitivity) or even of temporary gatherings of masses of people (e.g. rallies, open-air concerts, sport events, etc.).
Potential consequences of a drone crashing over sensitive places could range from interruption of an essential service for society (e.g. electric power supply), to health risks for the population nearby (e.g. in the case of chemical plants or reservoirs of flammable or toxic substances, or even only crashing over a crowd), to political issues or breaches to national security, as depicted in the following figure.