Too big to fail

If a company is "too big to let fail", such as Citi, AIG, GM, shouldn't we not let them get that big in the first place? I'm not sure they actually are too big to let them fail... But if the government thinks they are, then isn't the government negligent for putting us at risk by allowing these companies to get this big? Do we need anti-monopoly style laws to break up these giants early so that some can fail without government bailouts? If not, then these companies aren't too big to let fail.