I think that a National Day for prayer is more for the person who is slightly shaky in their faith. While praying for others is great and God answers prayers. I dont think He answers them according to how many people pray at the same time, I think He answers them as He sees fit for His good and perfect plan. Back on topic… I think a National Prayer day would strengthen the faith of others as you could witness how many other people out there besides yourself believe in what you. Its kind of an emotional support thing. Not to mention that other, non-believers could physicaly see the presence of the faith out there, and perhaps get the boost they need to attend a Church somewhere. Thats how I’d view it anyways.