If 2008 were an ordinary year — one during which iconic American firms like General Motors didn’t teeter on the verge of bankruptcy, the stock market didn’t lose a third of its value, and foreclosures, hemorrhaging 401(k)s and holiday retail blight weren’t in every headline — the precipitous decline of the nation’s newspaper business might have been the biggest financial story. Positioned at the intersection of commerce and mass culture, big daily newspapers for more than a century could outshine in popular cachet what they lacked in industrial size. Like movies, radio or television, they were part of the rhythm of American life. And like those industries, they have had to grapple over the years with new technologies that complicate their old business models: Radio bulletins made newspaper extras less urgent, for example, while the nightly news hastened the death of the evening paper. Neither of those killed the industry, though.…