I actually think its a non-issue really. When was the last catastrophic airship failure..1937 "The Hindenberg". The Stratellite does not use hyrogen as the primary lifting gas...Helium is used (non-explosive). And as many blimps covering sports events around the world every year....I have not heard of a major crash since 1937.
Even if there was a puncture, powerfailure, etc., the Startellite is designed with motors and airfins, and is designed to be flown to an extent. So even if massive systems failure, it could be brought down in a controlled glide. JMHO...but I think fears of an airship :crashing" down on people can be easily alleviated.
And I'm with Rock on the Airbus A380...would hate to live in the flight path of that monster.