There is a legitimate company which cracks passwords for a living (internet security company). In a demonstration of their methods they said they would take twenty people, have them fill in a form, and they would crack half their pin numbers (bank card) from the form. The form had questions like "your age", "address", etc. One of the questions asked people to fill in their pin number. 25% of people actually filled in the very thing that the company said they were going to find out. This either proves that we are dumber than we thought, or that this company managed to hypnotize twenty five percent of the group.