The top programs (BM, Goucher and Scripps are the most familiar) always lose 1 or 2 people over the course of the year, but never many more than that. And usually it's not for academic reasons. People find that they aren't personally invested enough to continue with all the BS, or they decide another career is best for them. Come to think of it, I can't think of anyone who desperately wanted to be a physician and just couldn't finish one of the formal programs. Everyone I know who peaced found something that interested them more. Good for them.