I avoid processed chocolate and make my own from cacao nibs and cacao butter. This removes some potential concerns about quality, rancidity, and additives. Cacao is mostly half fat and half carbohydrate (by gram, not calorie), with some protein. The fat is half saturated.
Cacao has large amounts of some minerals like Mg, but a large amount of phytic acid that will inhibit mineral absorption. It also contains other phytochemicals that many people claim is good (anti-oxidant, etc), but I think most of those claims are on shaky ground. It also contains substantial amounts of theobromine (very similar to caffeine). There is a history of large amounts of cacao consumption in healthy cultures in Peru, which have lead to claims of health benefits of chocolate based on epidemiological evidence. Chocolate doesn't seem to be a paleo food- it requires fermentation.
Is chocolate a food of healthy cultures? Is it an optimal source of minerals, a compromise dessert, or bad for you?