It's really famous with movie/porn sites.
You rank on Google for "watch harry potter free".
and on that page you make them, fill a surver/CPA offer before they can watch the movie.
The actual movie may or may not be there, the content has to exist depending on the network you're promoting.
Example networks: CPAlead, BlamAds, etc
Obviously there are twists to this method and the traffic source but I'm leaving that out on purpose.