Geofj,
If you think it's so easy, try this two-minute demo/test where you are presented with actual Xray images and have to find the threats in real time. Your performance is graded at the end.
http://www.msnbc.com/news/729756.asp?cp1=1
The link takes you to a story, just click the "Interative Can you spot the threats?" link in the right column.
A couple of things you should know about the test results that you quoted.
1. The tests were conducted by people who are completely familair with the procedures in use and the limitations of the equipment so they are able to conceal the test devices so as to minimize the chance of detection. The testers also know all of the profiling criteria so are able to avoid the extra checks. (About half of the 9/11 hijackers were flagged by the profiling in use at the time for additional scrutiny. They didn't have any prohibited items in their checked bags so those extra checks didn't find anything. Today being flagged would trigger the hand search of the luggage which would have found most of the missed items in the test.)
2. The tests were conducted prior to the TSA taking over airport security. Those results will be used as a baseline from which improvement can be measured.
Last I heard, the TSA had hired close to 1000 supervisors who were in the process of being trained. Those supervisors will go out and hire, train, and supervise nearly 30,000 new screeners later this year.