Wendy Roth was recently interviewed - and her research was featured - in an NPR article discussing the impact that DNA ancenstry testing kits (particularly their affordability) has had on the U.S. Census.
From the article:
"In and of itself, [a DNA ancestry testing kit] doesn't tell you your race or ethnicity," Roth says. "What these companies are telling you is that you have a likelihood of having a certain amount of your genetic markers associated with certain populations more often than others."