While security through obscurity shouldn't be relied upon, obscurity does play a part in security (You don't go around publishing your private keys, for example, and you don't share your passwords). You'd be foolish to think that narrowing down the vector of attack won't help.
Physical security works in a similar manner. You have multiple obscure parts (keys, passcodes, etc), and non-obscure parts (locks, cameras). If I have keys and passcodes, and I know where the locks are and where the cameras are, I can get through. And, it's not incredibly difficult to get a key (I have personal experience with this, hence the specific setup). What saves you is the passcode and camera that aren't known. That, and the fact that the guy was half-drunk as it was.
In the end, you don't rely on obscurity, but you don't go out of your way to tell everyone what you are doing. That's why you pay experts to do it for you.
> "obscurity does play a part in security (you don't go around publishing your private keys...)"
Security by obscurity is the opposite of using private keys. The algorithms for security by public/private keypairs are published and open to anyone to see; the strength does not depend on keeping the algorithm secret.
(Worth mentioning, some public/private keypair algorithms may actually have security by obscurity built in, such as the DES algo that some people speculate has hidden backdoors in how hashes are created.)
Thought it was obvious by the phrasing I was using, but apparently not. The obscurity part is keeping the private key hidden. The password unknown. The key in your pocket.
> the strength does not depend on keeping the algorithm secret.
And as for the security measures that he "won't put on camera because that would be insecure"... wow.