A study at Harvard University shows that Adult Entertainment internet usage is very high in some of the most conservative states. The linked article tries to make a correlation between Porn and Religion, as well as Democrat vs Republican voters. The actual study seems to be a bit more fairly balanced.
It still does put a correlation on religious aspects (in table 4) and tries to come up with some explanations. I think the reason for it in these states is that it is less socially acceptable to physically go out to a store and purchase these products than it is in the other states. Although there are a lot of inconsistencies. Maybe people
Will you buy porn tonight?: Study maps porn usage. (via windycitizen.com)