My take on the whole fellowship question is this: all fellowships are not equal.
For example, some fellowships train you extensively for specialty surgery. For example, transplant surgery, plastics, advanced laparoscopy, CT... These fellowships take your general surgery training several steps beyond what you learned. In these fellowships, you are really learning new skills that general surgeons probably did not aquire in their residency.
Other fellowships are more of a marketing tool. For example trauma surgery, "breast fellowship", colorectal, surgical oncology, and perhaps even vascular (although with the new emphasis on endovascular treatment this probably belongs in the above category)... These fellowships give you much more exposure to fields that are already covered pretty well in the general surgery residency. So, if you plan on an academic career, then you probably need a fellowship in these fields as both a pedigree, as well as additional training to strengthen your skills. And if you plan to go into private practice as say a "critical care" surgeon, or a "breast" surgeon, a fellowship is more of a marketing tool. You can say, I am a "colorectal" surgeon and get more referrals for colon CA. Or you can say, I'm an "endocrine" surgeon and get a lot more referrals for thyroid and parathyroid cases that might otherwise go to an ENT guy. Though really, if you went to a balanced surgery program and got balanced experience, then you should already be able to handle these surgeries, and be able to build your practice accordingly whether you have a "breast fellowship", or not.
Just my take on the whole fellowship thing... It seems like the trend is for people to do more and more training though...