http://www.washingtonpost.com/wp-dyn/content/article/2007/09/21/AR2007092102347_2.html
...Homeland Security Secretary Michael Chertoff in August 2006 said that "if we learned anything from Sept. 11, 2001, it is that we need to be better at connecting the dots of terrorist-related information. After Sept. 11, we used credit-card and telephone records to identify those linked with the hijackers. But wouldn't it be better to identify such connections before a hijacker boards a plane?"