BU isn't particularly honest year after year regarding the size of the waitlist. It's apparently VERY large. I even hear that that no one is rejected for the March decisions. Every year, Witzburg gives his famous speech about hating wait lists and wanting to keep them small so that there's a reasonable chance that everyone on it will eventually get an acceptance. But come the end of March, everyone not accepted is waitlisted.....It was that way last year and the year before as well.
The waitlist could still definitely move, but for the past two years, it hasn't moved at all...
btw, I was waitlisted by BU last year....