Keith,
In this case, Homeland Security did not use the information they had to protect its citizens. First step is to create (if they haven't already) a computer program to coordinate incoming information and red flag potential problems.
The airlines, in this case, had a cash paying customer on an international flight with no luggage. They should have caught this. Again, a simple computer program or properly trained agent could have red flagged this passenger.
Funny how they instantly know if I short changed my income taxes by $15 but haven't the ability to keep a mass murderer off a plane despite numerous warnings.
I think my biggest complaint is the innate complacency of those claiming to protect us. They usurp one privacy after another and then lose sight of the real threat. This will happen again and we will have another September 11. Meantime, we will be fed a lot of platitudes about how it all worked out OK because Tom from Sarasota jumped across the aisle, put out the fire and kept the terrorist in a choke hold.