Reading over some of the comments I agree with Samuel Walters and firehawk12. It bothered me while watching the film that apartheid was never mentioned. I'm not comfortable with the excuse of apartheid being solely represented by the aliens, so therefore you don't have to or shouldn't have address it in the film. I would've liked to have seen how the arrival of the aliens impacted the apartheid system. Why base it during apartheid era South Africa and not address apartheid?
I also had some issues with how blacks/Africans were portrayed. The Nigerians were depicted as savages and the few 'respectable' blacks-namely Wikus's chief assistant and the guard were clearly subordinates, with the guard even calling Wikus 'boss' all the time. That rankled me a bit. There were also scenes with blacks and aliens 'living' together or in proximity with each other in shanty towns, and it's never explained why is that, or why there were no whites living in those conditions. Except for the MNU representative and one clip of a female doctor, whites were clearly in charge in SA. Why is that? Apartheid, which was never addressed. Just not discussing it, or even mentioning, made me feel like the social conditions of blacks and whites in this film were just the way things were without any external causes and that didn't sit well with me.
Despite my misgivings I enjoyed the film, for what it was, but I think the avoidance of dealing with apartheid undermined the social message of this film. Overall I thought it was well written, well acted, the FX were good, esp. the prawns, and it's one of the better sci-fi films I've seen in a while. However, my enjoyment was dampened by the omission of apartheid and the depiction of blacks as a whole.