because you don't want to loan them, say, $5 billion to cover their toxic assets.
Then when they fail, and don't have enough money on hand (Federal Reserve rules allow banks to have only a few percent of the deposits in cash available), the FDIC will be on the hook for $18 billion forever gone, instead of $5 billion that will be paid back in several years.
It's either loan them hundreds of billions to keep them afloat, or let the FDIC come up 10 to 20 times the amount to cover the insured assets.
Yes, at the time deposits were insured for $100,000 or $250,000. Nevertheless, the FDIC usually covers the entire amount of the deposit.
That's what happened when they bailed out the S&Ls back then. Even though there were lots of accounts with more than $100K in them, and they were insured only to $100K, the federal government decided to cover the entire amount on nearly all of them.
As a real world example, Bank of America has deposits of more than $800 billion ($775 billion before the merger with Merrill Lynch). How much money did they get from TARP? Less than $60 billion.
So, loan them <$60 billion via TARP, or allow it to fail and have the FDIC be on the hook for up to $800 billion in deposits.
Your choice.
Further reading:
http://www.marketoracle.co.uk/Article4335.html<snip>
The 1.22% Reserve Ratio means that for every dollar in your bank account, the FDIC has 1.22 cents “in reserve” ready to cover your potential losses. This has proved to be an ample amount during the period of stability we've recently had, but it doesn't seem particularly significant, considering the recent headlines about banking losses (Spring of 2008).
Consider, for a moment, the collapse of Bear Stearns. In order to assume that bank, JP Morgan asked for, and received, a special waiver from the Federal Reserve to keep $400 billion of suspect of Bear Stearn's assets off the books of JPM (page 4 of the linked document). While JPM may have been padding the books a little bit here, due to the uncertainty of how bad the wreckage might turn out to be, $400 billion dwarfs the $52 billion reserves of the FDIC.
If one medium-large bank collapse could wipe out the FDIC by a factor of nearly 8, what do you suppose would happen if there were multiple, simultaneous bank failures? At this point, my guess would be that Congress would be sorely tempted to borrow additional funds to remedy the situation, but I worry that hardship and losses might result while the laws were amended and sufficient funding avenues identified. So how many bank failures could the FDIC endure? The data suggests slightly fewer than one big one.<snip>
This is also where the phrase "they are too big to let fail" came from. They knew that the FDIC didn't have enough money to cover even one medium to large bank failure.