- ACW: Two armies, roughly equal in strength and technology, from countries of roughly equal size and strength, fight a war that consists of a series of massed battles that are fought in territories belonging to both sides.
- Boer War: A large, well-equipped empire fighting against a smaller, less well-equipped civilian militia, in a war fought in and among the homes of the guerrillas, far from the center of power of the empire.
- The generally parched appearance of the landscape in Firefly.
- The existence of slavery (mentioned in the series, even if not explicitly shown).
- The fact that the people on the border worlds are depicted as scratching out a living in a place where they are and have been for some time rather than as expanding into new territory.
- In Our Mrs. Reynolds, the colonists in the first scene look (if memory serves) rather like old photographs of Boers.
The logical consequence of this, I suppose, is that at some point after the BDM there will be a major war between the Core Planets, with the border planets being used as pawns.
ETA: Well, apparently this theory is completely blown out of the water by an interview Joss gave a number of years ago. I still think it's an interesting theory, though.