If, like me, you're used to believing that you get at least a modicum of security out of the locks on your doors, this video on "bump keying" will leave you a little queasy. It appears to be1 news footage from the the Netherlands showing a frighteningly simple technique for hacking all kinds of mechanical locks. It features a lock hacking group, who are apparently trying to get publicity about this because they think people are at far greater risk than they know; they've written a paper on the technique as well, that's referenced at the end of the video.
It's hard to say what's most disconcerting about the video, but there are three good candidates: the simplicity of the technique; how quick and unobtrusive it is; and the susceptibility of even some quite sophisticated locks. The technique is essentially to cut an appropriate key blank down to its full depth in each position, insert it in the lock, and tap it sharply while twisting. Apparently the inertia jogs the pins out of the way. The basic technique has apparently been known for around fifty years, but the Dutch lock hackers have discovered refinements, which they believe are also known to criminals, that vastly improve its effectiveness. Read their paper for a detailed (though quite accessible) discussion.
1 It's a video from the Internet, so you have to consider the possibility that it's an hoax. But I've been on the net for over fifteen years and this looks as legitimate as anything I've ever seen.