Spoiler at the end; anyone going this deep this late in this thread without reading the Sprawl Trilogy deserves whatever they find.

They come dangerously close to calling Firefly cattlepunk (I confess the idea had occurred to me) and based on the fervor of Firefly fandom and many steampunk fans reaction to cyberpunk discussion, that's VERY dangerous indeed.

It's not always easy to determine what is and isn't cyberpunk; attempts to pigeonhole ironically blur the lines of demarcation. The Net was on a few hours ago; some might be surprised to hear me say I think it's more cyberpunk than the Terminator movies are. Certain ingredients are necessary for cyberpunk, and make it possible in any setting. The biggest is a noir society with powerful (though not necessarily malevolent) organizations, where trafficking in often proprietary data is integral to and fundamentally alters that society. Anywhere with espionage lends itself to this, because it's populated by jaded characters both moving a lot of critical secret data and employing a lot of it for the cool special gadgets associated with cyberpunk (it's important we don't put the cart before the horse here; cool gadgets are a SYMPTOM of cyberpunk, not a basis). Ian Fleming and Tom Clancy don't qualify because their protagonists usually work overtime to PREVENT secret new tech from fundamentally altering society, typically in nasty ways and/or on behalf of powerful malevolent organizations. You could make them cyberpunk with just a few tweaks though; cyberpunk owes as much to noir spy novels as it does to noir detective stories (whose cops, mafiosos, hidden weapons and mysteries thus also naturally lend themselves to cyberpunk, but unless the Maltese Falcon has the cure for cancer inside it's not a paradigm shift constituting cyberpunk).

There are also certain totems of cyberpunk, superficial side effects easily mistaken for core attributes, but they merit comment perhaps more for to avoid that mistake than to aid identification. Computers are the most obvious; good period cyberpunk exists with computers created by Babbage, Da Vinci, Merlin and [your polymath here]. Stephenson could do a stonepunk prequel to Snowcrash. The gadgetry I've already mentioned. Sprawls, megacorps and/or true dystopias are common in cyberpunk, but not NECESSARY. "Vanilla" cyberpunk is almost by definition set in the imminent future. The main thing to remember is that none of these phenomena are unique to cyberpunk; the determining factor is whether they function as part of a cyberpunk structure or a different kind of fiction. The presence of an AI doesn't make 2001 cyberpunk, nor an Aston-Martin turning into a jet make Bond cyberpunk, nor Coruscant make Star Wars cyberpunk, etc.

Here's an amusing question: Does the fragmentation of the Wintermute/Neuromancer entity into sub-entities who deny and ignore their parent prefigure the fragmentation of cyberpunk into derivatives that do the same...?