They bought Country Wide and Merrill Lynch at the behest of the feds. In return for that 'favor' we guaranteed billions in worthless assets they purchased in the deals.
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Calling BS shopper.
BofA bought Countrywide on their own in January of 2008.
The Bush administration bailed them out when the Countywide loan portfolio went south.
Merrill Lynch probably had more to do with BoA heading south at least according to the SEC.
Legal Briefing: Bank of America Shareholder Lawsuit Over Merrill Lynch Merger Moves Forward - DailyFinance
Bank of america shareholders sued Merrill Lynch.

The FED was heavily involved in that purchase. They had to approve the deal, and did, despite opposition by stock holders. They knew CW was going down, and BofA was one of the few banks that could handle the losses they thought CW would take. In the end, everybody miscalculated. That's when BofA started to unravel, so the FEDs came in and propped them up.
BofA was the "dumping ground of last resort" for the FED. In doing so they've created a monster. We either nationalized or vaporized a lot of the losses.
Remember the FED buying up 1.25 trillion in MBS recently? They manufactured that money out of nothing. When the value dissapears, that excess cash will be running through the streets of the economy. Nobody knows who sold to the FED, but you can bet BofA was at the top of the list of sellers. (edit - oh, and take a guess as to what they might be buying with all that excess income.. treasuries. The circle of collusion is complete.)