I'd bet the pendulum swings more towards the other side, though (as in people come in wanting to be surgeons and then change their mind; I know my med school class was like that).
I totally agree - I think that people who wanted to do medicine, and then switch into surgery, are in the minority in many schools. I think that the opposite is much more likely. There are definitely many people in my school who fit your description - heck, that described 3/4 of the boys on my surgery rotation!
Just to give the opposing point of view on that whole "keep your mind open" schtik. There are a lot of advantages to knowing what you want to do early. Granted, you have to be flexible on some level just in case you really hate it, but the truth is at some point you're going to make a decision.
True - but I think that the advice of "getting published early, make mentors early, etc." is valuable to all students, regardless of the specialty. As they say, it's better to shoot for derm, and then love peds, than the reverse. I'm still grateful for the advice I got from the internal med and family med mentors that I met during first year.
But going into medical school fairly convinced that you're going to do one specialty can bite you in the butt, too - I actually think that it can be much worse than the reverse. Lots of people who remain open-minded until halfway through third year manage to match well - but there are a surprising number of people who remain stubbornly fixated on one specialty, and DON'T match well.
I think the biggest danger (for me, anyway) of fixating on one specialty is that I kept trying to talk myself out of other specialties, or try to convince myself that, no, I REALLY DID love internal med/family med - that my enjoyment of surgery was "just a phase".
It didn't dawn on me that I was lying to myself until I was scrubbed in on a case, and I was disappointed that the case was over. That's when I realized that, actually, I didn't want to do internal med or peds.
The same thing is true for the opposite. There's a guy on his medicine rotation who kept insisting (half-heartedly) that he truly loved surgery. Halfway through, though, he realized how much he loved medicine, and had to admit that maybe he isn't meant for surgery after all.