Quick - name a surgeon general.
Dr. Koop? That was easy. Name another.
Sorry, Elders didn't get the job. Got a second? I'm waiting....
Perhaps I'm being unfair in your case, but we've really only had one celebrity Surgeon General. And since Koop retired, Presidents have seemed happy to keep it that way. So, other than to provide fodder for bad jokes, why is Obama apparently choosing somebody who is already a celebrity for that job?
I suspect that there are several reasons, but that they all tie together.
Gupta has incredible media access and connections. When he makes an announcement, he's pretty much guaranteed that it will get ample news coverage.
He has a popular persona of being trustworthy and competent. He has already been introduced to the American public, and he has an established, good reputation.
When necessary, he has enough personality and public access to bypass the media and take his message directly to the public.
Despite his relatively conventional choices for most positions, I personally expect Obama to follow the model of his campaign, using community organizing techniques and Internet outreach to bypass traditional media and even political channels, in order to get public sentiment behind proposals that face opposition - Republican or Democratic opposition. In that context, with health care reform being an exceptionally thorny and controvercial subject, Obama's choice of Gupta makes perfect sense.