"In a remarkable 36 hours of his presidency, Barack Obama carried a momentous secret and gave no hint of it as he consoled tornado victims...What few insiders knew was that Obama gave the go-ahead Friday for the military operation that would end with the death of terrorist leader Osama bin Laden..."
he probably kept it quiet because he either didnt know it was happening until after it was carried out ! or more likely he didnt say anything incase the inteligence/operation went wrong, especially considering the pakistan government didnt know that the american team was on their soil or that any such operation was being carried out, a little embarassing for pakistan !! but not as embarasing as it would have ben if it went wrong ! so dont make it known publically untill you know its gone to plan .
it ia also reported this was a kill not capture operation, why? why not capture him and bring him to account for his crimes, just as saddam was and enevitably what will happen in time with gaddafi ! (tho it was reported on sky news that osama was asked to surrender twice before being shot)