[thatmariolover]

Yeah.

He supposedly has a skin disease called Vitiligo (Vit-uh-lie-go), as Kitana already pointed out. For people with dark skin pigmentation, the disease really stands out. In some cases, the disease can spread to parts of the body other than the places you first have them. Such was supposedly the case for MJ. So he decided to go through with a special bleaching proceedure to make his skin a consistant color.