I was just accepted to a grad program for fall of 2011 where I was considering concentrating in Public Sociology. Coming from someone who loves sociology more than oxygen, I have to say that the infighting going on regarding public sociology is a huge turnoff. That being said, I still find the idea of public sociology very interesting. I've always been frustrated with the fact that academics acquire so much knowledge but tend to just sit on it. I know that there are professors and academics who utilize their expertise in non-academic areas, but for the most part I find their talent wasted. Even when groundbreaking research is found that can be used to better a given agency, the information takes too long to disseminate. That's what lured me into public sociology - the idea that I could use social knowledge and apply it to the public.
I totally understand the point about public sociology not having a clear mission, but that might be a good thing after all. Any attempt to better society through social research is subjective to the person interpreting the problem. Keeping the mission open restricts the subjective nature of public/political activity.
I just read something by Mathieu Deflem from USC, who seems to be very up in arms about public sociology. He makes some very valid points, although many of them I think are stemming from the fact that he doesn't understand what public sociology actually is. That and I think he just has some serious issues with Michael Burawoy and he's taking out his anger on public sociology.
Very interesting topic though.