"What happens when the same number of people pray for something as pray against it? How does God decide whose prayer to answer? Does the total number of people praying for or against something matter? How about the righteousness of the supplicants? Are positive prayers answered more frequently than negative ones? Does God take the positive ones and Satan the negative? Does the intensity of the praying have any effect on the outcome? Does the length of time one devotes to praying have any effect on the frequency with which one's prayers are answered? Do the words and phrases used in the prayer — either positive or negative — have any bearing on the success rate? Does the nature of the thing or things prayed for have any bearing on the prayer's success rate — either positive or negative prayers? Why or why not??"
Robert A. Baker, "Prayer Wars" Skeptical Briefs (http://www.csicop.org/sb/9709/baker.html, Septmber 1997).Via Pharyngula.