Reuters: The Coast Guard is scrambling to prevent a giant slick from an oil rig blowout from reaching the U.S. Gulf of Mexico shoreline, Coast Guard Commandant Admiral Thad W. Allen said on Wednesday. “This is potentially a very serious issue … We are under no illusion of the risk that’s involved here,” Allen said. He told reporters in Miami the Coast Guard, working with federal and local authorities, had activated contingency measures aimed at protecting at-risk areas of the coast …