Where the cloud touches down is not just the business of the geeks. Data centres are essential to nearly every industry and have become as vital to the functioning of society as power stations are. Lately, centres have been springing up in unexpected places: in old missile bunkers, in former shopping malls—even in Iceland. America alone has more than 7,000 data centres, according to IDC, a market-research firm. And each is housing ever more servers, the powerful computers that crunch and dish up data. In America the number of servers is expected to grow to 15.8m by 2010—three times as many as a decade earlier.