Mark's right, some types of companies should not be allowed to go public. The conflict between client service and shareholder profit is too strong in fields like investment banking and health insurance. Indeed, I think health insurers shouldn't even be allowed to be private for-profit companies. Failure to commit to short-term shareholder gain will get you sued. There's no way this can ever be a good thing.
Mark also points out a big common factor between AIG, Lehman Brothers, and Merrill Lynch: all three failed companies burned enormous amounts of capital to buy back stock from shareholders earlier this year. If I blew my allowance foolishly on Monday, why should my parents bail me out on Friday?