Treasury Secretary Timothy Geithner says government will spend up to $100 billion to join private investors in buying up to $1 trillion in bad sub-prime mortgages, securities and other ailing assets. The Obama administration today formally unveiled details of its long-awaited plan to help cleanse banks and financial institutions of bad home loans and toxic securities, making a calculated gamble that partnering with private investors to buy the assets will stabilize the crisis while limiting the risk to taxpayers.