Where do they get their ideas?

I always assumed that writers based their work on their experiences, history, dreams.. etc.. and that the product that came from that would be meaningful in that way to them. So how to understand where people come up with screenplays like 'Hostel'? I mean, it is a pretty sick idea to formulate, that people would actually kipnap other people for the sole purpose of selling them to the highest bidder to be tortured and killed in some sick attempt to live out a sick fantasy. That's pretty damn twisted. And the person who thought it up?? *shudder*

I wish I could ask .. who is it Tarentino? or Eli Roth.. I think he was the writer. Anyways. How do they cook up this stuff? And is it really a good idea to put together such clever little plots and give the real life sickos ideas? I 'm not one to blame crime or violence on media alone.. but a disturbed individual can get a hell of a lot of ideas from movies/television. I even think sometimes that shows like CSI only further enable them to comitt crimes by pointing out weak spots in a 'plan'. Maybe I am being ridiculous.. but I don 't think I'd want to worry about whether or not I was part of some criminal's gameplan by providing ideas.

I just watched Hostel., again.. and I am officially TERRIFIED to ever leave North America. Other movies, such as Wrong Turn or Texas Chainsaw Massacre offically have me scared of Hicksville, USA. Maybe I should just keep me and the kids in our happy little Ontario bubble...