Cluin, I agree there's no need to white/black up--IF! That is, IF the actor can carry it off in the context of the play and the production thereof.

But it is only realistic to realize that audiences are part of the equation too, and they bring baggage with them. With all the best will in the world, they have experiential expectations. And I'm not talking about racism here, I don't think. But it seems to me that a "barefaced" black Hamlet in an otherwise white production is in all likelihood going to be starting in a hole in trying to create the illusion. His blackitude, to coin a term, is going to keep sticking a visual contrast in the audience's eye. A great actor just MIGHT make them forget it, but it's an uphill battle.

Seems to me, if you have a powerful, famous black actor whom you'd like to see dealing with the emotional problems of Hamlet, you should also cast the King, the Queen, and the ghost with black actors. If you want Ophelia with a black actress, you should also cast Polonius and Laertes with black actors. If you want to give equal employment opportunity to black actors in Romeo and Juliet and don't want to black up or white up, make either the Montagues or the Capulets a black clan, and the other clan can be white, or oriental if you like.
As a side benefit, it will help the audience keep the sides straight, which can be a problem with big Shakespearean casts.   

To hark back to my previous entry, an unmitigated white Porgy can deal a blow to the story's verisimilitude.

Dave Oesterreich