There is also the matter of cost-benefit analysis of time spent updating passwords. Where I work we have a special code that has to be typed in by logged in me

There is also the matter of cost-benefit analysis of time spent updating passwords. Where I work we have a special code that has to be typed in by logged in members of the team if they want to really delete a transaction, this code is the same for all members of the team. A manager sets this code to expire on a monthly basis because a new code will be good for security, apparently. In reality this means that on the first of each month a team are locked out for an hour or two whilst the new code gets generated and circulated - in email. So there is a misunderstanding on security plus an implementation issue leading to disruption equivalent to the loss of a person's productivity for a day. A similar scenario of disruption happens if you use lots of devices and need to update a password on several boxes to get working again. There may not be the communication overhead of my special code analogy (which is invariably delayed due to waiting for the manager to get out of meeting), however there is still disruption and time taken out from the task in hand. As an aside, I like 'ambient' passwords, e.g. the VAT number on the receipt that you got given buying your lunch, the receipt can be kept in the top drawer - safe from the cleaner - and, if it is lost, you can go to the shop again to get another receipt.