Prime Minister David Cameron says the delayed response by London police helped lead to Britain's worst riots in decades. With 16,000 officers on the streets today, London was quiet, but other parts of the country saw looting and violence, and ethnic tensions are rising. There's debate about root causes. One target is Cameron's "austerity measures," which are cutting both social services and budgets for the police. There's worry about the future, and Cameron is talking with US police, who have experience with criminal gangs. And, while London has already finished the venues for next year's Olympic Games, will it be safe enough for visitors from all over the world?