This is an interesting question that a few of us residents were talking about the other day. We couldn't fathom lengthening our residency by another year to do more of what we've done in general surgery residency.
What does a colorectal surgeon do that a general surgeon doesn't? Maybe more APRs, more inflammatory bowel disease (and they can have that), and more J-pouchs.
What does a "laparoscopic" surgeon do that a general surgeon doesn't? Nothing. Our general surgeons do bariatric, nissen's, heller myotomies, nephrectomies, adrenals, appys, choles, and colons without ever having done a fellowship.
What does a surgical oncologist do that a general surgeon doesn't? Surgical wise, nothing. But these guys are probably a little more involved in the chemo/radiation aspect of things and doing a little more research.
So what's the answer? After talking to some staff who did these fellowships, I think the answer may be that they would like to funnel their practice into one area. This keeps them sharp on that single area and helps avoid consults in other areas of general surgery that they may not want to do. The problem is that sooner or later, you have to take general surgery call and revert back to performing the other cases.
General surgery is definitely not dead by any means. Jobs are abundant. Smaller communities (<70,000 or so) are dying for you to practice with them. In larger academic arenas, classic general surgery is definitely more of a rarity.
I have no idea what the most popular fellowships are. I would definitely say that anything that improves your lifestyle seems to be popular (i.e. Plastic surgery, laparoscopic, etc.) Critical care also seems be getting some notoriety for its lifestyle post fellowship.
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