AIG was the borrower (and separately Fannie and Freddie), banks were the lenders, it is absolutely useful to think about the situation in those terms. It highlights the conflict between our political intuition that insurance should be protected and financial speculation should not - some people thought AIG was doing one, some people thought the other. Likewise some people thought Freddie and Fannie were widows-and-orphans investments that the government should guarantee and some people thought they were private financial traders. Clarifying these things could have averted the crisis, it's absolutely a useful model.