We found this study on Gawker that involves pornstars and some surprisingly in depth stats on the adult industry:

• The most common bra size is 34B, and most female porn performers are brunettes.
• The top porn star-producing state is California, which has birthed four times as many porn stars (939) as its next-closest rival Florida (at 216). (After Florida come Texas, New York and Ohio.)
• Internationally, Hungary and the Czech Republic follow the United States as the most common birth places of porn stars.
• The most common role for women in porn: "teen." Followed by: "MILF," "wife" "cheerleader" and "nurse."
• The average age of performers playing "MILFs": 33. Only 7 percent are over 40 years old.
• "Butts," and its synonyms, appear in porn titles twice as frequently as "boobs" and its synonyms. Peak butts was reached in 2006.

See the whole survey here.