Though Mr. Sosa has claimed that the cream he uses is a "skin softening cream that...has bleached me some." (Sammy Sosa Admits He Bleaches at Bossip), he then admitted, in the same breath, that it is a bleaching cream he applies every night. He also claims not to be a racist, though I wouldn't quite assume that of him. I would only assume that his mind has rejected as much melanin in himself as the bleaching has - proof of the long-standing faction of discrimination among dark-skinned Spanish-speaking islanders refusing to be identified as "Black". I would also guess that it has something to do with the way the Dominican Republic treats its neighbor, Haiti.
Though one of the biggest celebrity instances of skin bleaching in our decade, Mr. Sosa's case is just an example of how popular bleaching creams have become since the era of the "Peola", or the Tragic Mulatto. The concept then was that people of mixed race (mostly women) would usually try to "pass for white", and disinherit their black family. They would marry white - rich white, usually, for they were always portrayed as beautiful - but when they had their children, the other half of their ethnicity would be discovered, and the women would suffer at the hands of the white people she thought had loved her. Within the sphere of acting, women such as Fredi Washington (the original "Peola" from the 1934 film, "Imitation of Life"), and Lena Horne lived this role to a minor degree - an "acknowledged black" was not allowed to play a white character, no matter how light-skinned she was, until around 1950. In some of their films, these women had to apply make-up that would actually make them look "blacker", so that their race would be known to audiences.
However, in the world beyond film, many "mulatto" men and women attempted to "pass for white" in their society, employing the use of bleaching creams and hair products to do so. Today, hair weaves, relaxers, colored contacts, and those same creams are used by black people all over the globe - as this family in Jamaica explains.
For further research, before moving on to other (more socio- and psychological issues concerning bleaching creams in the African-American society), check out this series of videos on a documentary which relates the skin-bleaching fad to Indian (Asian) culture and the complexities within.
P.S. - if you haven't already, check out the show "Black.White", produced by Ice Cube. While furthering the discussion about Bleach Creams as a problem, we'll also talk about the lack of racial sensitivity within both sides of the spectrum - that putting on a mask does not make you something else. That the "acting black" and "acting white" stereotypes don't actually make sense. Stay tuned.