A reader has an interesting point:

1. Why is it illegal for me to pay a prostitute for sex, but it's NOT illegal for a film director to pay two people to have sex in front of a camera and then make money for his product in the form of a DVD or an online download? 

2. As a corollary: Why are a prostitute and her john held in such contempt by the media and the public, but Jenna Jameson and Ron Jeremy are treated as rock stars on both cable and network television? Are they not prostitutes? They were, in actuality, paid for sex. No?

A thought experiment: if you hired a couple to have sex in your bedroom while you watched, it would be prostitution. if someone else hired them, put it on video and you watched them in your bedroom, it would be porn. Why is one illegal and the other isn't?