Every game I've ever played in, and every game I've ever run, has had dragons as epic forces of Good/Evil, that dwarfed the power of mere mortals. Up until about 15th level or so, an encounter with a dragon was one where you considered yourself lucky to escape alive, never mind defeating it single-handedly.
What would a campaign be like where the main enemy was dragons? Since dragons scale through jsut about all experience levels, PCs could be fighting them almost exlusively from the beginning, instead of, say, goblins. Assume that Dragons are prolific enough that wyrmlings are a dime a dozen, even if they get progressively rarer as they go up in age category. Could you build a game around that? It completely destroys the image of dragons being epic adversaries, for one thing.
Or does it? If you spend your entire adventuring career fighting a particular Great Wyrm's hellish spawn, couldn't an encounter with the Mother herself be pretty Epic? What do you all think?
If this is too much of a thread-hijack, I'll start up a new one.