http://www.straightdope.com/classics/a970912.html
Cecil, and the person who asked the question, both seem to have the idea that “Fan Death Phenomenon” is exclusive to Korea, but I’m afraid not. I was recently borrowing a couple of fans from some locals (I live in Beijing, China) and they warned me: “Do not sleep with these fan on, because it very bad for body. You can die!”
I didn’t want to ridicule their beliefs since they were lending me the fans, but I just had to let the Doper community know that this UL has now reached the largest nation on earth! I’m sure Laundry Ball companies around the world are scrambling to set up shop in this rapidly opening market 
— G. Raven