A short story by Orson Scott Card in his collection Maps in a Mirror. The protagonist specialises in psychological password cracking; by finding out as much as he can about a person, and if necessary meeting them, he can often determine their password. (These are 15-character passwords and the account will be locked if the wrong password is entered three times.) A suggestion I've heard for defeating this type of cracker is to produce a list of 100 passwords by whatever method you like, then use a random number generator to pick one.