A few days ago, a caller to a radio talk show mentioned that he was a frequent flyer. And he has two artificial hips. Every airport he'd flown from his hips have set off the alarm on the screening devices - that is every airport he's flown from *except* Kuala Lumpur - which he'd used twice. If security is that lax we can assume terrorists are aware of that fact.
PS: re my YouTube query above, I've now re-set my privacy parameters but my Favourites are still available for the world to see. (Only a problem if you've set up your YouTube using your given name.) I wonder how many others are unaware that their history is public. Could lead to some embarrassing revelations.