[Modernman]

I would say, there is certainly a difference between porn and erotica. Porn, to me, involves overt sexual acts. Erotica is more subtle- Vargas pinups from WWII are certainly erotica, but they aren't pornographic.

[Phantom Lord]

Thats fine, but again, it all depends on who is writing the definintion and making the laws. There were attempts in WWII to prevent those pinups as they were "pornographic".

[Tailgunner Joe]

They are also not forms of prostitution.