"What happens if you give a thousand Motorola Zoom tablet PCs to Ethiopian kids who have never even seen a printed word? Within five months, they'll start teaching themselves English while circumventing the security on your OS to customize settings and activate disabled hardware."
Michael Howard said something years back that stuck with me - programming is human against compiler, much easier than security which is human against human.
Of course in this case its not a classic security fail of a malicious threat against asset, in fact the overall story is quite a triumph of human ingenuity:
"We left the boxes in the village. Closed. Taped shut. No instruction, no human being. I thought, the kids will play with the boxes! Within four minutes, one kid not only opened the box, but found the on/off switch. He'd never seen an on/off switch. He powered it up. Within five days, they were using 47 apps per child per day. Within two weeks, they were singing ABC songs [in English] in the village. And within five months, they had hacked Android. Some idiot in our organization or in the Media Lab had disabled the camera! And they figured out it had a camera, and they hacked Android."
What it does show from a security perspective though is the limitation of what we can reasonably expect from any access control. Humans with time and determination will find their way around, whatever you're basing your access control scheme on (TLS, Kerberos, SAML, ...) you have to assume it will fail eventually (and not in a good way as in this story) and factor in how the system as a whole survives.