As capeman pointed out, the FDIC will borrow the shortfall from the Treasury (We the People, that is). Then, in theory, the FDIC will levy increased deposit fees on the banks (as they are doing now on a regular basis) who will pay back the Treasury and replenish the fund over time. I think the Treasury will get paid back and the insurance fund will be replenished but it will take many years. And who will pay for this? Depositors, ultimately.