Is the downgrade of the financials warranted?

In short, no. The downgrade of the investment banks just doesn't make sense. Why? Simple. With access to the Federal Reserve's credit facilities, the same facilities made available to the commercial banks, these investment banks have access to plentiful, and cheap, capital whenever they need. A credit rating downgrade, by definition, presumes that the ability of the entity being downgraded to satisfy its debt obligations has somehow worsened. The fact that these banks now have access to more, not less, capital directly contradicts this action by the ratings agencies.

So, then, why did they do it? Good question - I'm not sure I know the answer. The consensus, however, seems to be that the ratings agencies are late to the game and are now reacting to popular fears that have all but disappeared since the first fall-out from the collateralized debt obligation defaults and, more recently, swap defaults and associated insurance scandals. Furthermore, the spotlight that was placed on ratings agencies following the aforementioned collapse when they did has placed the integrity of their models and practices into question. It could very well be that they are now simply trying to follow the herd rather than lead.