Some developing countries either have no ATMs, very limited ATMs, or are not connected to the international networks. This includes Myanmar in Southeast Asia, as well as parts of Africa. In Japan, most bank ATMs don't work with international cards (the cards are even an incompatible size), so you need to look for a post office, 7/11 or Citibank ATM. In certain countries, not every ATM accepts foreign credit or debit cards. So check in-advance about what's available, and do what's necessary to ensure you have adequate cash during your travels.
What is the best source of information for finding out about ATM availability? I am travelling around Europe (including Eastern Europe) and trying to figure out what card/card(s) to obtain to make sure that I am never caught without money.