I heard about a research project a few years back where people were offered pens in return for their passwords. I managed to track down a link with some vague details. Check out Demon’s news page (new window).
The basic jist of it is, 75% of people asked gave their password in return for a pen. A further 15% gave their passwords after some persuasion. So in other words, 90% of employees would give away their passwords in return for a standard ball point pen. Fantastic!