This article brings up a good point regarding getting a better offer when you've already committed to a school. Gotera makes the claim that even if you've already told a school you would go, they won't want a hesitant or unhappy PhD student to attend just because they got trapped. Chances are, if you already committed but get an offer from your top choice, the school you said you would attend will understand and that spot will go to an ecstatic waitlisted student.
http://www.uni.edu/~gotera/gradapp/results.htm
Greetings, I am a longtime lurker and a member of the waitlisted! My cycle has essentially ended with three MA offers and one PhD waitlist. The MA offers have not provided funding information yet and so the potential for a PhD and funding is far more tempting. I didn't receive anything wicked specific but their first email sounded very pessimistic. Following my response, she replied with a much more upbeat sounding email where she asked me to stay in touch and let her know if I responded to other schools. Of course, tone can be tricky to interpret in an e-mail so my perception could be wrong. Regardless of the seemingly large number of people on the waitlist, I would say that making it onto the waitlist for such a small program is in itself a small victory.