When Biz Stone, a co-founder of Twitter, relates the story behind his iconic venture, he likes to use a picture of a flock of birds. The reason? As Stone tells the story, he first appreciated the power of social media a few years ago, when he watched a crowd suddenly arrive at a bar after exchanging messages on a phone. That event, Stone says, helped him to understand how social media enabled people to suddenly congregate with unforeseen speed and force. To put it another way, what 21st-century tools do is enable people to “flock” together – around ideas, emotions, places or events. Hence that picture of birds.

It is a thought-provoking image, and it feels particularly pertinent to New York right now. Last weekend I hunkered down, along with millions of other New York residents, as the tropical storm-cum-hurricane known as Irene ripped along America’s East Coast. In some senses the experience turned out to be far less dramatic than many had initially feared: though the East Coast was battered with powerful winds and lashing rain, and there was terrible flooding inland, New York itself suffered far less damage than predicted. Before the storm hit I moved out of my apartment, which is next to the river, to stay with friends elsewhere. But my girls and I slept soundly during the night (much to the fury of my daughters, who were hoping that the winds would wake us so they could hold a midnight feast).

While Hurricane Irene might have spared New York in physical terms, the experience was nonetheless striking, for reasons that Stone observes. In earlier periods of my life, I have experienced moments of adrenaline-fuelled anxiety, holed up in a hotel in the middle of a civil war, or marooned in a remote outpost by snowstorms. Those occasions were marked by long spells of boredom, punctuated by flashes of anxiety, since I was dependent on a crackling radio or creaking telephone for news.