So Mozilla has recently mentioned that system integration is a key goal for Firefox 3. Rather predictably, they don't talk about integrating with Linux at all, just OS X and Vista. Judging by the comments to the blog post, Linux users appear to be miffed about this.
Which is odd, since this is a hole the Linux community has dug themselves. Listen, I know that software diversity is a strength in many ways, but the fact is it comes with some downsides. Even whittled down to the major ones, Mozilla would still be looking at integrating into 5 or so distros, some of whom have 2 (or more) desktop environments for a user to choose from. Oh, and they're supposed to do this for a tiny fraction of the desktop market.
Bottom line? Saying that the Linux market can't justify the investment, and that in any event even if they did make a theme it couldn't possibly fit every Linux anyways is perfectly valid. And to act like they've somehow dropped the ball because they aren't willing to spend money to develop styles/themes for you to use for free makes the community sound a little spoiled, doesn't it?