Of course, black (or generally - non-caucasian) models are discriminated in the fashion world, that's the fact. And now, after the famous statement of Naomie's, that "fashion favors fair skin", the discrimination became the "it" topic in modeling. And so now we've got more and more black girls in the magazines and on the covers. Here are some examples.
Don't get me wrong - I really think that diversity in fashion magazines and in fashion in general is a good thing. But the diversity we have now is not a result of real tolerance, but a-few-months-lasting trend. Speaking of myself, I would really like to see some Asian or Latino faces on the covers, but what I am left with, is just waiting for another trend to come.
The situation reminds me of politics towards Chinese government. For years and years people around the world were aware of the situation in Tibet and nothing had been done. Now - with the Olympics starting - so many people are protesting against the discrimination in China. Again - noble reason, but still just a trend.
(On the other hand, don't you have this impression that lack of well-known black models keeps Campbell in the industry?)