A couple of thoughts on this;
1. Scenario: an evil person prints up thousands of Justin Bieber t-shirts with "By wearing this t-shirt I freely give my soul to Satan" written in an obscure language and very small letters on the hem of the shirt. The evil person hands out the shirts for free to all the kids attending a concert. Would Satan be able to claim those souls or would God protect them since God knows what is truly in their hearts? I strongly believe the latter. God
knows.
2. Take heart in this survey:
http://religions.pewforum.org/reports
While belief in traditional dogmatic religions have waned, most people still have spiritual beliefs, belief in an almighty power. The number of atheists (the "When you're dead, you're dead" crowd) remains about the same at 1.6%.
Most people believe there is something more to existence than simply the physical. While they may not believe in stories of ancient miracles and the hard and fast rules laid down by Moses 3400 years ago, but they know there is something to it. They can feel it.