While that possibility does exist, I have a gut feeling about the probability of that ever happening and my feeling is that the chances are pretty slim. Having grown up in the era of strike-anywhere matches, I know of no one personally who has ever had any kind of a mishap such as unintentional ignition. I will acknowledge the possibility that during some forms of motorized transportation of these kinds of matches that there is the possibility of a vibration node being set up in a narrow range of resonant frequencies that could cause sufficient friction between the match and striking surface (they are not guaranteed to be in close enough proximity to make that likely in any event). But carry on one's person would serve to damp any such vibrations during motor transport and the whole vibration thing would never be an issue if the subject was walking or using non-motorized transportation. So how else would they unintentionally ignite within a match safe? In a sealed match safe, the limited amount of oxygen available for combustion would likely limit the amount of damage that could be done outside the match safe. Matches could be packed in the safe with cotton balls for filler so that movement within the safe would be further limited or eliminated altogether.