Risk-free interest? In a bank? Are you kidding?
If you pick a large bank, your deposit is within the limit for federal insurance, I guess you could say it is risk-free.
So, if the FDIC runs out of money (because of multiple bank-runs), the U.S. government will print as much money as necessary to cover the FDIC deficit, thus making the taxpayers pay all the debts.
How do you figure taxpayers pay?
How dare you ask me questions now having not answered my own?
But never mind, I know that you can't answer anything coherent, so it doesn't matter. Regarding the taxpayers money, it is called socialization of debts, when ordinary people ("taxpayers") would indirectly pay for the bank debts by lowering their standard of living through inflation since the government would print money to cover the debts (this is called seigniorage, i.e. "a right of the lord (seigneur) to mint money" from French).