It strikes me that the definition of Steampunk is rather a flexible one, due, in part, to the word "punk" having a more politicised significance in British English than it does in American. I was in my mid-teens when the punk movement railed against the established order back in the late 70s, and my generation still retains the attitudes that were formed back then. To us, the establishment was bigoted, brutal, uptight, and clearly representative of everything that is wrong with imperialism, market-driven policies, and the non-distribution of wealth.
Steampunk is, for me, the perfect arena in which to explore socio-economic policies that seem to have spiralled farther and farther out of control since those punk years. The capitalist system, in divorcing itself from social responsibility, has so undermined itself that people are now waking up and fighting back. The people who led us into this dire situation have been exposed as money-grubbing, self-serving, power-hungry, corrupt criminals (if not in legal terms, then certainly by any moral standard).
This situation throws into stark relief the benefits and iniquities of Empires—whether they be economic, political, geographic, religious, or a combination. Empire can offer individuals a sense of belonging and "place" by assigning them to a "class," but this necessitates making and maintaining distinctions that—through being defined by, among other things, economic benefits or the lack thereof—become increasingly radicalised, so the "upper class" gets ever richer, and the "lower" ever poorer.
Steampunk explores the manners and mores of such socio-political systems, and the propaganda and attitudes that maintain them. However, it does so in rather a playful manner, as if laughing in the face of their utter collapse. To borrow from Moorcock, Steampunks are "dancers at the end of time."
Steampunk mischievously takes once hidden motives and makes them overt, just like Wikileaks is doing. That's why steam technology has become our icon—its workings are obvious and understandable, in contrast to the esoteric nature of current tech, which is all internal and motionless. The contrast perfectly symbolises the socio-political struggles that we see in the world today.
Perhaps the best way to sum it up is to say that Steampunk knowingly—and in many cases unknowingly—draws inspiration from the current zeitgeist, wherein the old order, which was based on a privileged few keeping the truth veiled for their own advantage while feeding deceptive propaganda to the masses, is being challenged.
And, of course, it's also damned good fun.
Steampunk will only become more relevant, as it continually reminds us that motives must be exposed, empire-builders are not heroes, and, though fights must be fought, good manners cost nothing!
This latter point, while tongue-in-cheek, is also important, for, the Victorian tip of the hat, curtsey, and "How do you dos" remind us that social systems require a sort of sub-language, involving rituals that "oil the machinery" of our daily interactions. As we attempt to reshape the world, we must also create new modes of such behaviour, based on a respect for one another that the current system has lost, so that whatever we create in its place will function smoothly.
Steampunk, in drawing from the past, thus points the way to the future.