I like the advice so far, and wanted to chime in that I think it is definitely beneficial to contact the professors. If you are planning to reapply, you NEED to know why you didn't get in the first time around. Otherwise, why bother to reapply.
Also, I can understand the concern some people might have that the professor could be flooded with responses, but I feel that it is the obligation of the school to provide you with some feedback considering the investment you made (both time and money) in applying to their school. In some cases where the professor might not be the best person to contact, I would bet that the professesor themselves would then just not reply or they will forward your e-mail. I can't imagine a professor would hold a grudge, especially when all you are asking is how you could improve your application.
That said, do people find it is benefical to contact the program coordinator? That is, if there is one. I think that would be the later resource if the professor did not respond.
Thanks.