Security is better increased by designing for how people actually behave. By recognizing that the real goal of security is to minimize the relative amount of unauthorized use. Although a system with extremely poor usability would certainly discourage unauthorized users, it is likely to turn off the target users as well. Random passwords are more secure. A system-selected password is more secure than one the user chooses.
Long passwords are more secure than short ones.
Forcing the user to change passwords frequently increases security. Requiring different passwords for different systems increases security. All of these statements would be true if we did not have to consider the human factor. Take a walk around any office in the world and you can collect as many passwords as you like by looking at the yellow stickies pasted onto terminals, finding the cheat sheet in the user's top drawer, or searching the user's hard disk for the file that inevitably contains all required passwords in one conveniently machine-readable spot. The only people who can remember many long strings of random elements are circus performance artists.