As mentioned on the Thom Hartmann show;

http://georgewashington.blogspot.com/2007/09/top-down-demolition.html

One of the main arguments defenders of the official story have made against the controlled demolition of the Twin Towers is that demolitions never start at the top of the building. In other words, they claim that demolitions always start at the bottom and proceed upwards.

However, a new video shows an example of a top-down demolition of another building: