Yeah, that's quite disturbing.
This PDF file is really interesting:
www.toool.nl/bumping.pdf
I tried it myself a couple of days ago with a standard lock I had laying around. Took one of the keys that came with it and filed it down with "key files" from a DIY store.
I couldn't quite get it to work with the "minimal movement" method described in the PDF (the lock I tested with is probably just too cheap), but it worked perfectly by inserting the the bump key completeley into the lock, pulling it out again by one tooth and then slapping it with my finger and turning it at the same time. Needs a bit of practice to get the timing right, but I can now easily open my test lock with this bump key, without any other tools needed.
Haven't tried it with real world locks yet, but with my test lock it's a nice way to make people go "hmmmmm"
