9/11 - what have we learnt ?

Its that time of year again when we reflect on one of the largest and most outrageous acts of naked terrorism to be seen on Earth.

So what have we learnt ?

Here are some of my suggestions:

1. That not everyone thinks Islam is the religion of peace, including some of the people who tell us that it is.
2. Society is vulnerable to those who are determined enough to make reckless attacks on it.
3. That a country can be invaded and its military defeated at little human cost to the modern attacker (though high financial cost), but it can be held without paying a price in blood.
4. Sadam Hussain most likely didn't have any WMDs, and our intelligence was either wrong or we were lied to.
5. Islam presents a cultural challenge to western society which western society is ill equipped to meet.
6. We need to make our infrastructure more robust and assume bad things will happen and we must cope with them. ( The UK Gov says its done this - Swine Flu and Foot and Mouth suggest otherwise ).
   

Any other ideas ?