At least the New York Times says so:

At Wacoal America, one of the largest bra makers in the country, 36DD is on track to replace 36D as its most popular size in 2009. (Three years ago it was 36C.) Bare Necessities, an online lingerie retailer, said 34DD was its No. 10 best-selling size last year, up from No. 17 in 2002. And this fall Elle Macpherson Intimates will introduce its first collection for fuller-busted women, offering cup sizes from D to G.

[Your Bra Size: The Truth May (Pleasantly) Surprise You - New York Times]