http://www.charlierose.com/guests/paul-volcker Investment banks are larger than commercial banks. Due to there derivatives connections. Investment banks are like bookies they hold the paper of the bet and make money on the spread, but if one goes bust the other side cant be paid. Therefore they cant be allowed to fail. What a nice business to be in !
What if.. - Housing market falls 20% - USA recession thats is a very hard landing Then.. Citigroup fails - 100 trillion ( dunno ) of derivatives..then what !!
simple: bernanke buys all the underwater mortgages, and prints 1 trillion dollars and hands it to citigroup. then market cheers about what a great job he's doing.