Check the awesome "how Stanford does its application process" link in one of the stickies. It even has a comparison chart of people's choices after receiving acceptances from Stanford, Harvard, and UCSF. IIRC they initially accept about 260 for their class of 100, and then take the rest from the waitlist. Vanderbilt is about the same, and they have gone from 20-40 deep into the waitlist (this from the mouth of their director of admissions).