It's about maximizing $$ made on each qualified buyer.
In SOME cases you can add to your revenue but in some cases you send the surfer off to a penis pills site that you make less on that converts shittier than paysites... I believe in many cases you can deter a potential paysite buyer into something that doesn't perform as well thus losing money.
I'd like to hear more opinions though about this - does it add or take away or make no difference.
If porn is your main product and traffic source - do you add:
casinos, pills, etc?