What causes brown spots on cauliflower?

What causes brown spots on cauliflower? Is it bruising, mold/mildew, or a chemical reaction similar to the green spots on potatoes?

Google didn’t turn up any answers that seemed credible.

I’m giving the one bump. If it starts to drift again, maybe someone can report it to give it a chance with the foodies in Cafe Society?

From here: http://italianfood.about.com/od/aboutingredients/a/aa022205.htm

Selecting cauliflower: The standard rules apply: unless you are buying one of the colored varieties, the florets should be a brilliant chalky white verging on cream, and quite compact. An overall grayish cast may mean exposure to light, while darker – almost black – spots are the beginnings of spoilage. If the florets have instead begun to separate, it is probably old and will have lost flavor. In terms of smell, it should smell crisp, with a slight leafy cabbage smell. If it smells pungent it will probably be quite bitter, and you should pass it by. Finally, if you scrape a fingernail over a floret it should feel firm and slightly crisp. If it’s soft it’s not good. When you get it home it will keep in the crisper section of the refrigerator for a couple of days.

It’s actually called Black Spot, http://www.omafra.gov.on.ca/english/crops/facts/crucifer_IPM/ccgal71a.htm, and is a disease of the plant.

Does it look like this? That’s downy mildew, caused by the fungus Peronospora parasitica.

While I’ve never seen one quite that bad, I think the downy mildew picture looks about right. The ones I see tend to have beige spots growing to about the size of a dime. Increasingly all the ones in the store are looking a little spotty :(.