Like saying "I don't beat my wife" Obama's "will not" statements regarding the inept attempted Times Square bombing puts the emphasis in the wrong place in his first two sentences (I humbly suggest) by inadvertently bringing to mind the fear factors rather than speaking from strength in the positive as he did with the second two statements, beginning, "We will..."
Obama said "We will not cower in fear. We will not be intimidated... We will be vigilant. We will work together." Public figures are taught to avoid such defensive-sounding soundbites or answers to reporter's questions and to, instead, state the positive, strong and pro-active mental image they want to instill in others' minds.
This is an uncharacteristic lapse in Obama's usual responses to situations.