Once upon a time the preacher said that it is God's will for his people to prosper succeed and achieve. In the last 20 years I've observed various Christian groups with various emphasises on money.
Experiment. Imagine that Nate Silver - perhaps the nation's most famous statistician - had made a conclusion about faith in God, the prosperity gospel, and whether it actually worked.
Scenario 1. a rigorous peer review double-blind survey of a large group of people, believing God desires his people to gain wealth has absolutely no effect on the finance of the people in the survey.
What would happen? Based on Christians response to science, they would find every flaw imagined or real in the survey. They would say you have to you have to believe (true Scotsman, anyone?) They would ignore it as persecution and discouragement. Maybe one in a hundred preachers would go back to the Word to see where they went wrong, if there was something they missed.
Scenario 3. a rigorous peer review double-blind survey of a large group of people, believing God desires his people to gain wealth has a notable positive effect on the finance of the people in the survey.
If the survey came out in favor of the prosperity gospel, you would see some churches once again hammering their brothers in the face about the love of money about God's desire for people to use their wealth for building his kingdom for ministering to the poor for missionaries. The secular media would probably go bananas trying to get the more established prosperity gospel preachers on to the electric circuits on to the talk shows and not just on Christian television. And a third group of Christians would go to bed that night get down on the knees and pray dear God why did you let this happen? Why do you let our gospel get hijacked by those who just see it as about the blessings instead of the relationship with Christ.
Doesn't matter if faith works as advertised? Of course it does! If we preach a gospel that does not match how we advertise if we over sell then we risk shipwrecking the face of those who wonder, if God doesn't do that in the tangible world how can we trust in the in tangible world with forgiveness of sins and eternal life.
Which brings us to the great dilemma of the faith preaching what happens when what you have believed for doesn't come about? It's hard to believe in miracles when you're walking through the graveyard.