This article on MSNBC.com is pretty enlightening. (Click post title above to read). When I read the part about PMS and cravings it made total sense. I know a bit about serotonin, and the fact that the amount of it is lower in women's brains during PMS wasn't surprising. Hence my need to eat (read: inhale, haha) anything chocolate around that time.
If I'm craving chocolate I always eat a little because I'll eat everything else and then have it. That being said, I keep a small container of 70% chocolate squares in the pantry. By savoring one small square I appease my craving and don't overeat in other areas.