In many ways, PIN codes are more dangerous than passwords. Everyone uses them for ATM cards, credit cards, even the hotel safe. If you are small business owner or travel frequently on business, stop and consider some of the risks associated with a PIN code.
Like passwords, it is a challenge to remember different PIN codes for our ATM and each credit card so human nature leads many of us to make them the same so they are easier to remember. Banks and card issues too easily enable this practice by allowing us to change the PIN code on a card to a 4 digit number of our choosing. Worse, many will use the same PIN code to unlock a smart phone. See the problem?
When traveling, or even out on public, it is all too easy to shoulder surf someone unlocking their smart phone. Having obtained a PIN, criminals now have an easy target for stealing a purse or wallet, and a better than average chance that the code obtained by shoulder surfing can also be used for the newly stolen credit or ATM cards.
If you must set the PIN codes for all cards the same, at least use a different code to unlock a smart phone.