I found this one in Wiki, under the subject laptop:
A study by State University of New York researchers says heat generated from laptops can significantly elevate the temperature of the scrotum, potentially putting sperm count at risk. The study, which included more than two dozen men ages 21 to 35, found that the sitting position required to balance a laptop can raise scrotum temperature by as much as 2.1°C. Heat from the laptop itself can raise the temperature by another 0.7°C, bringing the potential total increase to 2.8°C. Heating of the scrotum is known to cause temporary sterility in men.