Pretty much what the others say, I believe the stories. I am always in the habit of clicking "home" when I want to just leave a site myself and I am what you would call computer literate believe it or not.
Also many users are paranoid or are very turned off by something that in any way makes them believe "I'm going to have to pay for this to get anything" or "I am going to get jerked around" so they will just leave if anything makes them suspect this. It's possible they were on a dozen other sites with FPAs that just jerked them around and so they have a bad association with it - like a subconcious suggestion. Who knows though just what goes through these people's minds...