"For centuries, when Europe was the global center of Christianity, millions of European missionaries traveled to other continents to spread their faith by establishing schools and churches. Now, with European church attendance at all-time lows and a dearth of preachers in the pulpits, thousands of "reverse missionaries" are flocking back, migrating from poor countries to rich ones to preach the Gospel where it has fallen out of fashion."
Washington Post, June 11, 2007
It might be noted that they tend to attract immigrants who already are religious. And I reckon that most Europeans have become too skeptical for this.
On the bright side, notice that humanist groups are starting to spread in Africa. Some of the them request skeptical books, and I for one am going to send a few myself.