Mold freaks me the fuck out.
Mold is not unlike a tiny world that grows anywhere it damn well pleases. Mold has no regard for what it may grow on or whom it may poison. It is just this living parasite that envelops prey, feeding off of it until there is nothing left to eat, growing until it can grow no more, unstoppable and inherently dangerous.
Imagine if you will, a tree. Now this tree has roots that dig into the earth so that it can collect water and nutrients from the soil. The tree takes up a certain amount of space, some trees growing very big, but the tree has a limit to how far it will go. It will not take up all the soil.
Now picture a tree that has roots that go fucking everywhere! Now imagine other trees popping up from those roots and like some bushes and shrubs and shit, just popping up everywhere. Boom, tree pops up in the middle of your kitchen! Whooosh, shrub in the bedroom! Soon it is a world of greenery and the humans can do nothing to appease the horrible tree monster as it wants nothing other than to take over everything.
That's what mold does, but on a smaller scale.
Did you know that people can get mold on there bodies? I was once a told a completely unverifiable story about a guy who never toweled off after a shower. He just got out of the shower and whipped his clothes on and then, I guess, sat there is kind of wet clothes for a bit? I don't know. Anyway, he got yeast infection on his chest from it! GROSS! (On a some what related note, do not google image search 'yeast infection on chest' unless you never want to have a boner again.)
Now, I know what you're saying, most mold is harmless, just throw out your fruit when it gets moldy, why are you keeping fruit around long enough for it to get moldy etc. But it's not just food mold! Moisture mold is the real scary mold because you don't even know that it is there! Any of you fuckers that live in a building that is over ten years old, chances are somewhere in that building there is a downright insane amount of mold inside some walls. Seriously, knock down a wall, you'll find mold.
I worked in Disaster Restoration for a period of time, which was not as glamorous as it sounds. It involved cleaning up floods/fires/wind damaged things etc. Most often, it was a simple flood, like the basement just flooded or something. Sometimes they flooded with poop and poo-water. In many cases, the insurance companies covering the jobs took their sweet sweet time to give the go ahead to let us finish the job once the disaster itself was taken care off. So sometimes these soggy basements, soaked in poo-water, would just sit there for a month or so. Let me tell you: I've seen things that change a man. Poo-mold related things. And if there is one thing that my boss drilled into my head it was that that stuff will kill you.

It's caused by a leaky pipe or heating or poor weather proofing or any number of normal everyday shit like taking a shower. All that steam and moisture you make when you are taking a shower, it's seeping into the walls and getting all moldy and someday you're going to be carrying a big box and you'll trip and fall and put a big hole in the wall and all the little dormant mold spores are going to burst out like a Glade air freshener and you are going to breath them in and die and then you'll be like 'so that's why Jake was afraid of mold.'