Hi! What's with the cultish following? As could be said for most soaps, I find it grade b and poorly acted, for the most part. I don't understand...
Well, you asked, so bear with me through the boring bits.

Look at the people who protest World Bank and IMF activities. They often can't articulate what they're protesting against, but it ties in closely with the global heating problem: there's nearly unanimous consensus that it's serious and exacerbated by human activity, but governments seem powerless to act because corporations won't let them. On a similar note, the December 9, 2006 issue of New Scientist has an article about pollution causing massive "dead zones" in oceans, but again, governments aren't doing much as they're threatened by business interests.

Couple that with a perceived loss of our freedoms in the US and UK caused by the government's willingness to trade freedoms for apparent safety and you can see how individuals are feeling increasingly marginalized. Many feel that their governments are against them and that corporations are calling the shots.

So what does this have to do with Firefly? It perfectly ties into this. The "Blue Sun Corporation" can kill with impunity and the Alliance tries to dominate and control people (witness the reference to Malcom Reynold's "Social Control #" on one of the Alliance's screens). Since it's science fiction, it's an extrapolation of where we're going and since it's a western, it has the individualist appeal. The characters in Firefly capture the frustration many people feel with the events that are unfolding today. They don't trust their government and corporations are making their lives miserable. In fact, in the Firefly universe, it's often difficult to tell where the government stops and the corporations begin. It's tough to hit closer to home than that.

As for "poorly acted", we are talking about cowboys in space. This ain't Shakespeare :)
It's also the same appeal with cyberpunk back in the 80s and early 90s. Philip K Dick, William Gibson, and Bruce Sterling were preaching the same thing back in the 80s, and they seem to only have a cult following. It ain't Shakespeare, either, but it is accessible and hits close to home.
I actually had the word "cyberpunk" in there at one point, but I realized I was rambling for too long, as usual :)
The fact that they showed up anyway to speak with everyone who paid to be there really speaks to their character. It makes me love the series/movie even more.

And I am now officially an Adam Baldwin fangirl. *squee*