If you want to know what's going to happen to the big banks and investment banks, you've got to go back to early 2003, when the seeds of destruction were planted.
It had been a year or so since a couple of trillion dollars of investor wealth had been wiped out. The Dow was 8000 and dropping, and the stocks of big institutions from Citi to Merrill Lynch to Morgan Stanley were at multiyear lows. Bank lending was down, but no one was really worried. The old "borrow short, lend long and pocket the difference" game had been around for millennia, and banks had weathered worse than this mild economic slowdown.
What was not at all clear was how investment banks were going to make money going forward. Wall Street had piles of capital and no place to go. Stock trading and large parts of bond trading had gone electronic. Decimalization of the stock market wiped out markups. IPOs were down, mergers were down and, gasp, bonuses were way down.
Stocks were out and investors wanted yield -- safe, predictable returns -- but there wasn't much profit in that. Some, especially hedge funds and international investors, insisted on even higher yields than plain old government bonds.
So Wall Street, as it always does, gave investors what they wanted -- excess yield in the form of derivatives, asset-backed, mortgage-backed, collateralized debt obligations (CDOs), basically funky amalgamations of lots of other pieces of paper. Done right, no one but you knew how to value these exotic instruments, so you could mark them up way more than a penny and generate huge fees, profits and bonuses. Win-win.