Or, if the terrorists wanted to be assholes and say "Yea, we still exist," why not drive down the 91 or 205 or any other parking lot freeway in southern California and deploy fields of caltrops to flatten the tires of cars and bring half the state of California to a standstill? People would be very annoyed - more annoyed than having to take off shoes at the airport or having to chug a bottle of water to prove that you're not bringing chemicals on board a plane.
