I know lots of people must agree with David, because I see lots of black and white prints matted white. But you can in fact find fully archival museum quality matboard in black, though it requires some careful searching. That's my preference, and it's the only matting I use. My complaint with white matting is that it's like having a transparency on a light table without any mat. The glare around the image detracts from your eye's ability to discern detail. White matboard is like an overwhelming glare on any but the most high-key of images.

IMHO.