Exactly. There were 1.4 applicants for every spot in derm last year. Specialties in 2011 that were more competitive than derm: general surgery, internal medicine, orthopedic surgery, plastic surgery, and psych (for this one, the huge number of international applicants skewed this results). Looking at only US seniors, ortho, radonc, ent, and plastics were more competitive than derm (plastics by far being the most competitive). Neurosurgery was equally as competitive as derm, and internal medicine was only 0.1 point behind derm (for every US senior applying to derm, there was one spot available. For every US senior applying to IM, there was 0.9 spots available).
Last year, 48 US seniors with step 1 scores below 220 applied to derm. 21 of those matched. 13 with scores below 200 applied. 3 of those matched.
This is raw data from the NMRP. It says nothing about whatever attributes low step1 matches in derm had.
You can draw whatever conclusions you like from this data. To me, I think a reasonable person would see that someone with a score just below 220 who is deadset on derm does not have to abandon his or her dreams.
Additionally it's worth noting that derm is not the most competitive speciality in contrast to popular opinion. It's not even second or third or fourth. What is interesting and noteable about derm is the unusually high number of applicants with AOA membership. If you're not AOA, then you would probably be naive to think that you actually have a 50% chance of matching into derm with a 215 step 1. Your chances wouldn't be zero, but they would logically be lower.
And I think it's an exaggeration to say how big of a deal not matching is. That's person-dependent. It probably would be a disaster to the applicant with $400,000 of school debt with a wife and kids and no other discernible skills or job prospects. To an independently wealthy applicant with income sources outside of medicine, it's likely not as big of a deal, and the risk these two different applicants would be willing to accept in the residency match would be wildly variable.
In summary, I would be very cautious of blanket statements about test scores thrown out by people on the internet and use your own brain to evaluate your own personal situation, talk to your own advisors at your school, and make your own personal decision.