Certainly not at the top of your personal brand communications plan!
However, what he did was good personal branding. One of the very first exercises that I get clients to undertake and a core part of the personal brand building foundation is the Values exercise.
I describe Values as being your moral compass. The things that we stand by in all situations, or if they are being compromised either by ourselves or someone else it makes us angry or upset. You only have to see Greg Smith's outburst to understand that on some level his personal values were being effected by working at Goldman Sachs.
Now in reading the 'backlash' from his very public outburst there may be other underlying reasons for his departure. But none the less he finally reached a point where all the benefits of working there could not outweigh how he truly felt.
Was he wise to do it so publicly is a whole different conversation. It may well come back to bite him. But I wager there will be a company out there who will hire him because of what he said, it just my not be in investment banking!