i applied to, and i kid you not, ~20 programs last year (hey - the apps were free and the same everywhere!) and literally got waitlisted/rejected form every single one except one straight acceptance to a program at a top 5 graduate school..that's all it takes and it was an amaaaazing experience. best of luck. and also, don't be discouraged - these programs have all sorts of candidate criteria they have to meet through the NIH/NSF (who fund these programs) - such that the student is from a college without vast research opps, is a minority, hasn't had a significant research experience, etc. etc. so that makes it really difficult to meet these and therefore, get accepted!