A dozen Secret Service agents sent to Colombia to provide security for President Barack Obama at an international summit have been relieved of duty because of allegations of misconduct. A Secret Service spokesman did not dispute a tip received by The Associated Press that the misconduct involved prostitutes in Cartagena, Colombia, the site of the Summit of the Americas. A U.S. official, who was not authorized to speak publicly on the matter and requested anonymity, put the number of agents at...