I guess there could possibly be something growing on there that is not good but it would be a result of introducing a bacteria to the cheese from a dirty knife or some such thing. In and of itself, I highly doubt you could get food poisoning from some old parmesan.
My family and I have a tendency to eat some really crazy cheeses when we get together. We constantly try to one up the other and see who can find the funkiest ones. I love all the blue cheeses and also ones that really smell badly.
My sister recently went to France and they came back with some pretty crazy tasting cheese. I think I will head to the Cheese store and load up on some Xmas fromage.