vanillabean

Different types of plastics have different porosity. Harder plastics have less porous surfaces which makes sanitizing them possible.

That being said my grandparents always reused ziploc bags. They rarely suffered from any illnesses, let alone food poisoning either. So perhaps its something that could be a variable, but most reputable sources would suggest not reusing ziplocs used for storing anything but office supplies or toys.

BakerMum

Part of it might be the fact that when you are frequently exposed to sub-illness causing levels of bacteria, you become immune to it. Its this that is blamed for, in part, certain health problems today because we are so freakishly obsessed with cleanness.