Why is it bad to eat moldy food, what kinds of food can you eat moldy, can you eat moldy sour cream?

like I know the question may sound obvious, but there are MANY foods that people don't drink unless the food has gone moldy or equivalent; examples are Kombucha, Kefir, Blue Cheese and wine. I have some sour cream that just has a LITTLE spot of mold on the top, that is why I want to know about the sour cream.