The majority of the people I mentioned who are doing extra years are doing it for personal reasons (spouse is a fellow in another field, graduating next year, want to go on the job search together, etc). But I think in general, there's so much more to know than there was 30 years ago, in all of medicine. It's the trend across the board, in every specialty except I suppose FM and EM. A very large percentage of people pursue ever more specialized training, both for job security and personal interest reasons, and also because practicing in a very broad, "know everything" field is intimidating. Since our fellowships are so quick and since our 4-year residency is so very broad, I don't think it's necessarily bizarre to pursue 2 fellowships, especially if they're highly complementary or highly desirable. I mean, you can go through your 4 years and only get a 1-2 months' exposure to whatever your subspecialty interest is.