Americans are being left baffled by a bizarre phenomenon that is sweeping the US. Called "flash mob", dozens and sometimes hundreds of people are turning up in public places and carrying out wacky, pointless stunts. The mass mobilisation is organised by email - those taking part agree to turn up at a certain place at a certain time to carry out the act. They then disappear a few minutes later, leaving bystanders scratching their heads and wondering what was going on. 'Love Rug' In the latest incident, 200 people turned up at a bookstore in Cambridge, Massachusetts, and pretended to...