I honestly do not know how many profs "take" their students with them. Will may have brought his students along with him. When I moved, the students stayed put but I stayed on the dissertation committees to the bitter or not so bitter end. I did have three students close to finishing when I moved last summer (all defended last fall in dissertation-defense-athon 2012), but I did not have any more junior students. Why? Well, mostly because I already had more than my fair share of students at my old job but also because I was planning to leave and did not want to leave folks behind.
Still, as admitted students ponder which school to go to (and think twice, given all that we have all said about the difficult job market), I would focus less on individual stars and more on department depth and breadth. Why?
- Your interests might change so that the best adviser might be someone different.
- The person who you think might be a terrific adviser is actually a lousy one-- I was not the person most of my PhD students intended to work with when they decided to go there.
- The person might leave, retire, retire in place (stop accepting new students) or die.
- Many of your classes, most in fact, will not be with your expected adviser.
- You learn as much or more from your peers (who are learning from other folks) as you do from your adviser. I avoided the Americanist profs in grad school, but learned much from my peers who were Americanists. And this helped in getting different sorts of feedback on my dissertation, on giving me some ideas via osmosis when I had to teach an American politics class in my second job, and it helped give me some understanding of principal-agency theory when I need it the most.