I know of one case where a mobile crane took off on a sightseeing tour of
its own. It sneaked onto a nearby airport (through the fence) and into a
hangar (through the door) and mangled a new jet fighter against the inner
wall. The contractor was insured to about $2,000,000. Rumour has it he
went rather pale when told about the cost of the damages...

Cheers,
Fred