In Korea, secret PIN is often used to protect credit cards, cash cards, and bank accounts. Unfortunately, most people don't treat PIN as a personal secret and not only share it with others but routinely asks for it.
At Korean banks and credit card firms, application forms often have a field for the applicant to specify his or her desired PIN for the new account or card, exposing the PIN to bank branch employees as well as the data entry clerk. In many recent credit card and cash card frauds in Korea, secred PINs were provided by bank employees.
At Korean merchants, point-of-sale devices allowing direct PIN entry by customers are often not available. When a customer hands over their credit card to buy something, the clerk will not think twice about ask for its PIN. So PIN is given verbally, allowing anyone standing near to hear.
This is a huge problem that only a combination of education and biometric can solve since even smartcards need PINs.