Indeed, porn sites is much popular sites around the world and there also many anonymous accounts that are using just to access their accounts.
As a bitcoin user, I didn't see any negative effects on using bitcoin as a payment method for paying their subscription or registry, because when we used bitcoin for online transaction we can also anonymous and it was easily for transacting payments. If the bitcoins will used in porn sites as their medium, the bitcoin can be more popular and it increases the number of users.