You can open a kryptonite lock with a biro, which is most disconcerning, especially as I use one myself. The newer "New York" range is supposed to stop this problem, but it shows that nothing is capable of stopping thieves.
I have only just started riding again after 4 years off, but I remember back when I use to ride, you could get barcodes installed into the headset with satellite tracking on them, just the same as you can get with cars and motobikes. It wasn't that expensive either and while it doesn't stop them from nicking your bike, it can help bring these thieves to justice, whether it be by the cops or with an old steerer tube.