Usually the danger is that food debris or grease will collect in the crack, then it will carbonize over time, causing arcing and damage to the material. It will eventually ruin the microwave.
It depends on where the crack is, too. In some areas, a crack can allow microwaves to leak.
It would help if you could be more specific, and if you would give us the model number in addition to the brand (Samsung).
Thanks!
William E Miller † MicrowaveDisplay.com, March 2007
