Subterfuge

"individuals prepared to carry out terrorist acts are already in the country " DHS Secretary Napolitano

Of course they are,the US Government has made sure of this and it has more to do with subterfuge than incompetence.
They are in the country and the US Government let them in and they are not looking for them because they want more attacks so they can unleash their draconian and opressive thugs to remove the last vestiges of freedom and torment the American pubblic more.
This is why they give the Islamic terrorists already here room to roam instead of going after them and shutting them down.
They would rather abuse the average law abiding US citizen than offend the Islamic death cult.