Hey spymare,
I have developed this as a plugin included in a ChildTheme. Both watching the Ads details (contact info) and NOT using the Contact Form in the sidebar until you pay for a membership.
Three kind of payments/membership:
1. possibility to access the WHOLE content,
2. possibility to access the content of the CATEGORY you choose,
3. possibility to access the SUBCATEGORY you choose.
... see the screencast here (the screencast it takes time to load but it is interesting)
http://www.screencast.com/users/iopt...b-f7d45c73c311
And the site in order to test this
http://web6.ioptimas.com/
THE MAIN problem here is that users must find your content VERY interesting and unique or they'll click off the site (as jomarkosabel and rodeoramsey says)
Regards,