As per Wikipedia, a bank failure occurs when a bank is unable to meet its obligations to its depositors or other creditors because it has become insolvent or too illiquid to meet its liabilities. Since some banks, including the Federal Reserve, have a license to literally print money, most people think that bank failure is impossible. But since some banks over invest in hedge funds, high risk mortgages, or commodity markets, it can happen and it has happened.
Banks have been failing since they first incorporated, and the fiscal crises in the late 2000’s caused the failure of a number of really big banks, including Washington Mutual, Lehman Brothers, and Bear Stearns. And regardless of how many new acts are passed to try and insure banks limit their risk exposure or keep enough cash on hand to cover withdrawals or payouts in the case of a loss, banks will still fail. Regulators will never keep up with the new and inventive ways banks and investors will come up with to invest, and lose, money (and shady replacements for hedge funds and high risk mortgages will soon be on the way), and banks will continue to fail. Possibly even yours.
And if you depend on that bank for letters of credit and inventory based loans, this could be more of a problem than losing any cash above the FDIC (or equivalent) insured amount. Having your critical supply lines stop, your production lines go down, and revenue losses mount by the day as you search for a new bank, new lines of credit, and new inventory loans will be far worse than a short term cash loss which can happen anytime a market shift causes demand for a high-selling product to suddenly drop, forcing a fire sale of a large amount of remaining inventory.
And, as per the Wikipedia article, the failure of a bank is relevant not only to the country in which it is headquartered, but for all other nations that it conducts business with, especially if the bank owns investment subsidiaries in those markets. People are put out of work. The local economy drops. And everyone suffers. Yet another damnation waiting around the corner.