What Exactly Makes a Browncoat?

"Firefly went on the air a few years ago and was instantly hailed by critics as one of the most canceled shows of the year. It was ignored and abandoned, and the story should end there. But it doesn't, because the people who made the show and the people who saw the show (which is roughly the same number of people) fell in love with it a little bit too much to let it go, too much to lay down arms when the battle looked pretty much lost. In Hollywood, people like that are called unrealistic, quixotic, obsessive. In my world, they're called Browncoats." - Joss Whedon, "Joss Whedon Introduction", Serenity DVD