I just came up with this so I'm not sure how good this would work. I was in psychology and my teacher assigned a project that had to do with the psychology of advertising and the project is for us to make a cereal box and other crap. She suggested that if your target audience isn't kids then don't put a puzzle on the back but something like "Win a Date with..." and with that I started to wander off in my mind and thought why not apply that to the internet? So here's the method. Set up a fancy, somewhat professional looking landing page saying something like "Win a Date with Jessica Alba" and "To enter in the drawing please fill out 1 of these offers." or "To enter the drawing please fill out this offer." Something like that. And that's it. People will fill out the CPA offer and hope for the date but never get it.