Jon Wood of MMORPG.com covers Firefly in his weekly column. He has a particularly interesting point to make with regard to the amount of information already known about the setting:

I think that one season was enough to give the audience a taste of what the universe was all about, but leaves enough of the lore unexplored to allow the game’s developers the chance to stretch their legs and create some new and interesting content. In fact, it’s the short-lived nature of the show that actually gives the game a significant advantage over other sci-fi MMORPGs like Star Trek Online and Stargate Worlds, which run the risk of getting so bogged down in the lore of their television predecessors that the fans will pick the games apart and turn away from them.

Certainly, continuity is (or was) an issue in SWG, where the game was nominally set at one point in the timeline, but had ships from further on, and numerous other problems that were noticeable to fans.