I'm not sure that I see this polarization in terms of music critics. If you look at any recent 'Best of' polls in places like Pitchfork or Spin Magazine, you'll see a fair representation of black and white, hip hop and alternative bands, and there doesn't appear to be any tension or animosity between the two camps.

White artists appropriating black artists is arguably the foundation of rock and roll and probably much pop music that has followed. In that sense, it has always been 'black' but has traditionally only sold well to mainstream (ie. predominantly white) audiences when it came in a white package. We could go into a debate about how much of this is unspoken racism versus identification with the known vs. the unknown but I think we all might find this a little tiresome. What I think has happened in the past 10-15 years is an acceptance, by a generation that hasn't grown up with the same institutional racism as their parents, of artists who are not white and a further identification with these artists.

What's interesting to me, looking at the Billboard music chart (and aha, I recognize more than 1 song, which I'm not sure if I should be proud or embarrassed about, given the chart), and specifically the titles of the top 50 tracks, is the resemblence to disco era sexuality, be it implicit ('Lean wit It, rock with it', 'Sugar we're going down', 'We be burnin'), overt ('Touch it', 'Pump it'), or childishly overt ('My Humps', 'Ms. New Booty'). I think this is probably the main reason why 'black culture', with respect to brian's question, is at an all-time high.

Some might say this is a backlash to the puritanical political culture in the US at present but I think it’s actually quite simpler.

Look at the two bands that Derek mentioned--Nickelback and System of a Down. How best to describe their music? Angst-filled, whiny, angry, confused, brooding? Would you use the same adjectives to describe the music (not the figure, down boys!) of Beyonce or the Black Eyed Peas? Beyond the question of whether or not they are contributing anything positive to pop culture as a whole, their music sure is a lot more ‘fun’ or 'exciting'.

Other than the American/Canadian Idol contestants, who destroy the music of black and white artists with equal aplomb several times a week, I also can't come up with any near-credible white artists donning the 'street schtick' to any acclaim. I'm curious, though. Did you have any performers in mind when you asked the question?