Something I've also wondered. Peshawar in NWFP and Quetta in Balochistan seem to get attacked the most. Cities like Lahore, Rawalpindi, Islamabad and Karachi are not attacked nearly as much despite these being bigger and more important cities.
P.S- Rest in Peace to the deceased.
When these 2 cities are repeatedly attacked than why the sufficent security arrangement can be doen to protect them?