Nobody tell the TSA, but last month someone tried to assassinate a Saudi prince by exploding a bomb stuffed in his rectum. He pretended to be a repentant militant, when in fact he was a Trojan horse:
The resulting explosion ripped al-Asiri to shreds but only lightly injured the shocked prince -- the target of al-Asiri's unsuccessful assassination attempt.
Other news articles are here, and here are two blog posts.
For years, I have made the joke about Richard Reid: "Just be glad that he wasn't the underwear bomber." Now, sadly, we have an example of one.
Lewis Page, an "improvised-device disposal operator tasked in support of the UK mainland police from 2001-2004," pointed out that this isn't much of a threat for three reasons: 1) you can't stuff a lot of explosives into a body cavity, 2) detonation is, um, problematic, and 3) the human body can stifle an explosion pretty effectively (think of someone throwing himself on a grenade to save his friends).
http://www.schneier.com/blog/archives/2 ... omber.html