If you look at decision posts from past years on this site, you'll see that WashU waitlists a loooot of people (by what I've seen, much more than other schools). @lolToasty - I'd say they have so-called Tufts syndrome worse than Tufts itself. Many strong applicants seem to get waitlisted (or rejected) if they weren't able to demonstrate interest well enough.
@itenet: A waitlist isn't exactly a rejection, but you kind of have to treat it like one and move forward with plans for other schools, because it's impossible to know whether a spot will open and you'll be offered it.
I got waitlisted too, btw. Disappointing, but not terribly surprising (again, due to demonstrated interest).