Note a recent read on the CruiseCritic Carnival boards about passenger burning up the their stateroom with candles. They also got the bill for the repair$.
Fire is the biggest hazard on a ship because of confined spaces (fire consumes oxygen, and produces toxic smoke [you might even get burned]). Thats why no smoking in cabins aboard Disney, no irons, no popcorn poppers, and they even cook in the galleys with steam heat. Disney probably gets an insurance break over competing lines because of it