As we saw in London, where a car bomb was discovered and dismantled prior to explosion when paramedics kept their eyes open and a policeman did the right thing at the right time, vigilance and attentiveness can make all the difference.
6 Years After 9/11, the Same Threat – New York Times
The new estimate does cite some gains; known plots against the United States have been disrupted, it says, thanks to increased vigilance and countermeasures.But the new estimate takes note of sources of worry that have arisen only since 2001. The Iraq war has spawned Al Qaeda in Mesopotamia as the “most visible and capable affiliate” of the original terrorist group, inspiring jihadists around the world and drawing money and recruits to their cause. The explosion of radical Internet sites has created self-generating cells of would-be terrorists in many Western countries. Lebanese Hezbollah, rarely considered likely to attack in the United States, now “may be more likely to consider” doing just that in response to a perceived threat from American forces to itself or its sponsor, Iran.
Here’s a PDF version of the key judgments of the National Intelligence Estimate, July 20, 2007.