Every program is different I'm sure, and they probably vary year to year.
Just as info: When I externed at Michigan, they had a fellow who had just finished his residency months earlier. They supposedly had the following year already filled as well, but there was no fellow the year before.
I'm not sure about the circumstances surrounding any of it, but they're the real deal for oncology, so who knows how it all got put together each year, given a vacancy in the position at one point.
I'm the Michigan fellow until 2010, and (I think) the only one on this forum so I'll give my quick and dirty overview of places. Michigan is a 2-year fellowship in both ablative and free/regional flaps. They didn't take a fellow last year since they had transitioned from 2 residents per year to 3 and wanted to see how the case loads per resident were affected. I think they're plenty busy and could maybe afford a 4th resident. We're doing 2-3 cancer cases per week right now, some small and some big. 3 fibulas last month, radial forearm last week, pedicled lat today. 27 neck dissections in my first 6 months which is on par with other fellowships. I spend most Wednesday mornings in the micro rat lab sewing vessels under the microscope with a plastic surgeon who teaches micro to the OMFS residents, Plastics, etc. Some of the fellows from other programs spend a week with him 1 on 1 learning micro skills. Like most places, cancer and flaps come in waves. I have been pleasantly surprised at how busy Michigan is with cancer, since you don't hear as much about this fellowship. One of the reasons it's 2 years is because I will spend about 10 months rotating with radiation oncology, med onc, skull base, general surgical oncology, plastics, etc....nice for someone planning on academics. Ann Arbor is a great small town with lots for kids and families.
Shreveport is a 1-year fellowship in ablative and free flaps. The current fellow is a good friend and he says they're pretty busy. I seem to remember the case log I saw was similar to here at Michigan, but 1 year without off-service rotations. Shreveport is not the funnest city, but I could live anywhere for only a year.
Jacksonville, FL probably has the highest case load. Probably about 60 free flaps per year, about 50-60 neck dissections. Rui Fernandes is one of the nicest guys you'll ever meet. The residents love him and play intramural soccer with him on weekends. Jacksonville is not a bad place to live.
NYU- you spend 6 months in NYC and 6 months in India. The current fellow just came back from India and was incredibly busy doing 6-10 cases per week, some with free flaps. I think there are other fellows that rotate there, so there is a risk of the experience getting diluted if you're the 3rd person on a case. I'm not sure who is doing the free flaps in NYC for OMFS, possibly plastics.
Oregon- historically has been a 1-year fellowship in ablative only, although they have orthopedic hand surgeons who do their free flaps. Rumor is that they will soon change to 2 years and offer free flap training also. Dierks is also one of the nicest guys you'll ever meet. He has 2 other partners that do cancer also (one more than the other). 2 of the attendings are dual-boarded in OMFS and ENT. Portland is a nice place, but maybe expensive if you have a family.
Maryland is the one place that has accepted fellows years earlier than other fellowships. When I started searching for a fellowship at the beginning of my 5th year (of a 6-year residency), they had already accepted someone for my year. It's a 2-year fellowship with a 1st-year and 2nd-year fellow. Historically the 1st year does the ablative and the 2nd year reconstructs, but I think there is some crossover. They also rotate with a former fellow in PA who does laryngectomies and thyroids.
I don't know much about San Francisco. It's ablative only. Brian Schmidt is also a very nice guy and one of the smartest guys you'll meet. He has a busy research lab with some big-time cancer research at the molecular level. San Francisco is very expensive.
On one hand, cancer fellowships are not that competitive if you consider that few people are interested. On the other hand, there are only a handful of fellowships out there. Last year there were about 16 people applying for 6 fellowships, so I think the interest is growing in OMFS.