The arrest of al Qaeda’s No. 3 man, Abu Farraj al-Libbi, in Pakistan promises to provide new information on Osama bin Laden’s life on the run and deprives the terror network of its chief operating officer, according to counterterrorism and defense officials. Officials said that if al-Libbi chooses to talk, he is in a position to dish out valuable information about al Qaeda’s current structure, funding sources and attacks in the pipeline. And most importantly, he might provide information that could rekindle leads to bin Laden that have grown cold this year. Al-Libbi is potentially the best source of information...