This seems to be pretty old, but I only stumbled over it recently:
Just in case you were considering buying a Kensington lock to secure your laptop while you're away... don't. Some lock picker from toool.nl (Barry Wels, it seems) has demonstrated how you can open such a lock within seconds, using only a roll of toilet paper and some duct tape. Watch the pretty impressive video (7.5 MB).
Favorite quote from the video: ...so actually you're
militarizingminiaturizing the roll of toilet paper.
Well, leaving a laptop unattended in a "hostile" environment is always a stupid idea (with or without a lock, with or without a screen saver with password). One of the many reasons for that is that your box can be owned by an iPod within seconds if you have a Firewire port...
(via Boing Boing)
Update 2006-03-20: I misquoted. He said "miniaturizing" and not "militarizing". Thanks Michael Goetze.