I can speak from my own experience this year with Cornell. I've essentially been waitlisted, but it's a kind of economic waitlisting - the department doesn't make offers without financial support, and because of the economy, the support that I would've been offered just isn't there... and so, no offer. They'll let me know if the money appears (which, I assume, might happen if enough people opt out of their Cornell acceptances), but I'm not very optimistic.