do FDIC rules apply to each account or each banking institution?
It's $250,000 for each unique owner of an account.
For example, a married couple (sorry, Toddy) can have an account in the husband's name, the wife's name and a joint account in both their names and have the full $250,000 coverage on all three accounts for a total of $750,000.
However if either of the spouses has another account at the same bank, it won't be insured if the other 3 accounts are maxed out at the $250,000.
This can be done as many times at different banks as the couple needs to insure all of their balances at all the banks.