Open-plan offices offer few pleasures; one of them is snooping on other people’s browsing habits. When, years ago, I began working for tech companies in San Francisco, I noticed that my co-workers were always scrolling through a beige, text-only Web site that resembled a nineteen-nineties Internet forum. They were reading Hacker News—a link aggregator and message board that is something of a Silicon Valley institution. Technologists in Silicon Valley assume familiarity with Hacker News, just as ...