I spy, with my big eye

WELCOME to China, the land of video surveillance. Guangdong province boasts over 1m cameras. In 2010 the city of Chongqing, governed by the now-disgraced Bo Xilai, ordered 500,000. Other provinces have hundreds of thousands, according to Human Rights in China, an NGO. Video surveillance constitutes over half the country's huge security industry, and is expected to reach 500 billion yuan ($79 billion) in 2015. China will soon overtake Britain, with around 3m cameras, as the capital of video surveillance.

Yet China is far from alone. In many democracies surveillance cameras are multiplying, too. And face-recognition technology is proving a wonder tool for both governments and marketers.