That sounds like an odd performance request, but according to this story, he's onboard to perform at the Mandela's 90th birthday party this summer. The article doesn't speak too highly of Eminem and you can almost hear the detractors and gay rights activists who will probably jump all over this in South Africa. Eminem is apparently retired (he went into exile shortly after long-time friend Proof was killed in 2006) and the concert this summer will be his first performance of the year.
-Jonathan Cunningham