In the three weeks I have been back in the USA, I have racked up 39 credit card transactions (Christmas shopping plus road trip). For the previous ten months in Vietnam, I had two transactions. Credit cards are still not actively used in Viet Nam except by tourists at international hotels and hotel restaurants. Even high-rolling Vietnamese businessmen use cash for expensive business dinners and entertainment, pulling out bulging rolls of half-million VN dong notes.
ATM or debit cards are now in wide use in Viet Nam, but mostly for access to cash at ATM machines. There are still few opportunities for point-of-sale use of debit cards in Viet Nam. And the opportunity to use a Vietnamese debit card is limitied to ATM machines owned by the bank card issuer. There is as yet no interoperability between VN bank ATMs.
There is also almost no use of checks in Viet Nam either -- I am told that Vietnamese business pay their bills in cash, personally or by courier, rather than by checks transferred in the mail as in the USA. I have noticed a wide use of bank transfers. If I want to subscribe to a Hanoi newspaper, I need to have the subscription payment wired from my VN bank to the newspaper's bank account number.
This leads to the second difference between life in Viet Nam and in the USA -- personal security. The utility payment collectors come by our HCMC house every month to collect our payments for electricity, garbage collection, telephone, ADSL, and water services. We pay in cash, which means the collectors walk through the streets and alleys of Viet Nam carrying purses bulging with cash. The same is true of curbside motorbike parking attendants and bus fare collectors, flashing huge rolls of cash in their hands. There seems to be no concern for personal robbery since it is evidently a not a problem in Viet Nam. There seems to be few incidences of personal crime such as homicide or rape in Viet Nam (I need to do some research on this). On the other hand, crime against property is an issue -- I am constantly told to properly lock up our motorbike, and keep the house locked up when we are away.