He quotes bankers who say that such a guarantee might encourage more banks to lend to growth companies based on the value of their intangible assets, because the guarantee would remove much of the risk for banks.
First, although charities seem to add significant value at current levels of funding, there is no guarantee that any extra money will produce similar amounts of added value.
Not only is Tesla guaranteeing that resale value, but Tesla CEO Elon Musk is personally standing behind that guarantee to give customers absolute peace of mind about the value of the asset they are purchasing.
If enough people think Ackman is right, then the value of MBIA's guarantee will go down and its revenue will collapse, putting the firm into financial straits.