This is an important distinction that many people don't understand. All banks in the US, whether they are chartered by the federal government or a state, are required to have FDIC insurance. For credit unions, however, it depends on state law. Those chartered by the federal government (with "Federal Credit Union" in the name) and those chartered by the majority of states, are required to have NCUA insurance. However, there are about 15 states that allow credit unions to choose between getting deposit insurance from the federal government or a private company. Many choose the private company because it's cheaper.

There is currently only one private company in this market, which is called American Share Insurance, or ASI. To their credit, they appear to be very well run, and there is no real reason to doubt their solvency. However, it is obviously not as good as being insured by the government itself, since the government produces the money supply.

Private insurance companies have failed before. For example, in Rhode Island in 1991, a bank run led to the collapse of the state's credit union insurer. The state government eventually stepped in and all depsoitors got their money back, but in some cases it took years, and there is no guarantee that they would do so again.

I'm not trying to scare anyone, but if you open a credit union account, you may want to make sure that it has NCUA insurance, especially if you're depositing a large amount.