[GeorgeTH]

There are/were several sites who have tried this in the past, and all failed! Some still have a paypal button on their page asking for donations (until their account is closed...), but I never heard of any where it has really worked.
There's so much free porn on the net that you'll drive people elsewhere - and that'll be the end of it. The savy surfer goes to incredible lengths, like opening the source code of some high skimming TGPs to get straight to the links that way...