Why should people not pray to the saints? My Catholic friend says she is asking these people to pray (intercede) for her, and that it is just like asking a (live) friend today to pray for you. She asked me what I thought was wrong with that, and I didn't really have a good answer, apart from notions about not communicating with the dead -- though she points out that they are alive -- and that Jesus provides sufficient intercession (Heb 7:25). I couldn't quite refute the friend 'sargument, although I mentioned that one doesn't actually know the deceased saints personally, I like my friends better alive! Any comments? 

I think that praying to the departed is a nice idea—getting departed Christians on your side—and I don't see any way to prove that they don't pray for us. However, 1 Tim 2 states there is only one mediator: Jesus. Not his mother, not his apostles, not anyone else.

Prayers to/for the dead popped up in 2 Maccabees -- in the time between the testament. Calling upon the departed is fraught with difficulty. Hebrews 7 states that Christ is our intercessor. We don't need anyone else, any more than we need further "priests," since Jesus is our unique and great high priest.

On a slightly different note, those who pray to saints will insist they are not worshiping them—or the images and icons relied upon in devotion. But interestingly, when Catholic and Orthodox believers "venerate" or "adore"  the "saints" and holy images, they may be observed praying directly to them (not to the Father through Jesus). There is no difference when they are observed praying to God. "Adoration" and worship are muddled together; there is no practical difference.