It boils down to "90% of Steampunk is crud", of course, and over at Futurismic, Paul Raven's commentary applies the inevitable and immortal coda to that clause.
I enjoyed both articles, and my superficial summary should not be construed as a dismissal; both Stross and Raven do provide some analysis of why Sturgeon's Ratio arises.*
Personally, I think that Stross's issues arise because, as a writer, he sees "Steampunk" primarily as a literary movement. In contrast, Cory Doctorow of BoingBoing tends to approach it more as a design aesthetic, applying the craftsmanship, materials and visual motifs of a bygone era to both wardrobe and cutting-edge technology.
I lean toward Doctorow's view: the current "Steampunk Movement" is connected to the Maker Movement. Steampunk's central defining elements are artifacts that imply a backstory. The literature that actually provides a backstory is a secondary effect. Science fiction writers and fans do love to follow such implications reductio ad asburdum, sometimes to good effect—but they often stretch a simple premise to its breaking point.
However, none of that is the main thrust of this post.
You see, inevitably, when discussions of this currently-trendy subgenre arise, there's always someone who fixates on the word used to describe it, insisting that it's neither "steam" (being more often wood, brass, and high-voltage Teslary) nor "punk".**
After reading this tedious protest one too many times, I hereby affix thumb to nose.
Steampunk is Punk because, as a design aesthetic, it's rebelling against mass production and homogenization by reintroducing the idea of hand-crafted artistry to technological artifacts.
Steampunk is STEAM because of a literary device known as synecdoche, in which part of something is used to refer to the whole thing. "Steam" is a concise shorthand for "Victorian Era Technology", because it was, in fact, the dominant and most distinctive technology of the era. Tesla and Edison, fine; Nemo's electric batteries, fine; Cavorite, if you must -- but it was the steam locomotive and the steam engine that reshaped the human landscape. Moreover, it's a technology that has by and large fallen out of use in the present day; by contrast, things like electricity are far more prevalent now than they were then.
Of course, once you discover that the original meaning of "punk" is neither "mohawked rocker" nor "small-time hood", but "prostitute" ... well, then, the whole "transformation of the subgenre into the current trendy cash cow for skeevy publishers looking to milk a quick buck" just makes it all the more appropriate. As Mr. Raven points out, the same thing happened to both the "rock" and the "cyber" variations on the theme.
*A quick look around suggests that the "second artist effect" that Unca Charlie cites may in fact be a new and elegant coinage for a principle that has been stammered about in genre analysis circles for decades. Has anyone else heard that turn of phrase ere now?
**No, it's not just you. Or you. Or any of the many of you who think this is personally aimed in your direction.
Cross-posted to KDDR.