Once again, there is a lot of misinformation on here about waitlists. Just because you know of one or two or three students with multiple offers does not mean there will be movement on any waitlists. Many programs admit more students than they want to take, with the assumption that many will decline. So if a program wants a target class of 5, and admits 10 students and waitlists 2, you will need 6 people to decline before there is movement on the waitlist. Your best bet is to stay in contact with the DGA/DGS and ask about school-specific policies.
Also, DavidSpring, almost every student I know in a top program has said they made their decision around 14 April/15 April. I don't have a huge sample size, but I really doubt that things will change much this year. That's not say that that is right/wrong, but just to say that asking people on gradcafe to choose earlier is unlikely to have any effect on when most students will decide (esp. as most of these people are not on gradcafe and many will wait until the last second to pressure schools to up the stipend offer). It's probably best to plan what you would do in all contingencies, so that in the event you get off/don't get off the waitlist, you know what to do.